I didn't think about it in these terms back when I was playing the game in the early 90s, but now it comes to me as coming down to players choosing to embrace or ignore the conventions of the genre.
Limiting the discussion to what is seen in the films, we see Luke quite able to fool with his light sabre the instant it is handed to him, and we see Han able to use one to slice open a Tauntaun on Hoth. The actual use of the weapon is one of manual dexterity. Its use will be somewhat mundane, however, as the user will not be able to do the cool tricks they have seen in the movies.
To use one like a Jedi uses one (prediction, telekinetic throwing, blocking blaster bolts, etc) requires the ability to use the Force.
With these assumptions in place it is hard to say that a character cannot just pick up a light sabre and go. However, in the groups I played the game with, no one did this who was not a Jedi.
Being in Tune with the Living Force (Trust your genre, Luke)
The reason was simply that we felt it was a weapon tied to the Jedi. We felt they were not available on the open market, and we preferred to use weapons we could get better use of. In other words having my Outlaw and the other non-Jedi characters wander around with light sabres did not fit the genre. Sure it was possible, it just wasn't something that was done.
If this is enough of a problem for you that you want to create house rules to prevent it, I would recommend speaking to the players about that directly, and citing how it is not really in the spirit of the franchise. Just because a thing can be done, does not mean it will be done. This is a part of the roleplaying aspect of the game.
Not for sale at any price (Made by hand, custom orders only)
Going beyond what is explicit in the films (although it is referred to by the Emperor), we agreed with the idea that a Jedi makes their own light sabre. Unless they were to lose one in combat, have it stolen, or be defeated and the weapon taken, there was simply no way for one to come into someone else's hands. If this idea is a part of your saga, then it really reduces the likelihood of non-Jedi having them at any point.
This is just a reduction, as if a player wants one badly enough they will go out of their way to nuke the first Jedi or Sith they come across.
Everyone gets cut (Hokey religions and ancient weapons)
If you are not above a little realism in your Star Wars, then the concept familiar to blade students everywhere that 'everyone gets cut' can help limit the field of potential light sabre users to just those who have the courage and the dexterity to do it with a reasonable chance of success.
This also is a means to reduce their use, through fear of personal injury. Although the rules do not support a lot of detail in the death and dismemberment department, this roleplaying aid can greatly enhance the mystique of light sabres and make playing a Jedi worth the hassle.
Guilt by Association (Isn't that a Jedi weapon?)
As the weapon itself is an iconic representation of the Jedi Order, who are outlawed and under an execution order (death by Vader) by the Galactic Empire, drawing attention to oneself through the use of such a weapon can be a great hook to get the story moving into high gear with detention cells, torture, escapes, chases, and other Star Warsian fun~
Consequences for action are nice as they put choice in the hands of the player. Rather than getting into a "I don't want you to do that" situation if that would be a problem in your group, you can limit the use of light sabres simply by making them logically, and socially problematic to use. Luke was willing to draw attention, live away from society, and fight the Empire head on. Plus, he was a Jedi. Are you?
When diplomacy fails (Shut up, Goldenrod)
As with any discord at the table where interests, enjoyments, intentions, and the like come into conflict communication is always the first step in resolving it. The suggestions above are intended to be used in conjunction with establishing what the genre of the saga is, which aspects of Star Wars the whole group wants to explore and which aspects they do not, how much realism there should be in terms of consequence (Luke lost a hand, Ben died, Lando got kissed by that lippy pilot, Chewie never got any pants, every custodian in both death stars was atomized, Jabba was strangled in his own ride, etc), and what play style (mission oriented, sandbox, scenario-based, campaign-based, etc) is to be used.
Each person should contribute ideas about what they do and do not want to be a part of the game - this includes the GM. If non-Jedi using light sabres bothers you to a great degree, express that clearly in the simple terms that it impinges on your ability to have a good time with the setting.
If they counter with 'just wanting to have a cool imaginary toy' and 'what's the big deal, anyway?' you have an impasse.
If the players do not care or think you are going too far in feeling that using an elegant weapon from a more civilized age when not a Force Sensitive is a problem, it might be a good idea to consider their point of view. Their lack of consideration for yours notwithstanding it never hurts to reevaluate your own position.
If you are the GM and you still want to stick to your guns on the issue, then I recommend choosing to continue the game, choosing to keep quiet about them using light sabres unsafely, and follow through on sensible reactions from the universe: NOT vengeful ones; that leads to the dark side. The dark side has no retirement plan.
- Do not allow cool Jedi sabre tricks without the Force. The rules
support you on this.
- If they operate where there are troops or other law enforcement
personnel, and get spotted using light sabres, have them be
investigated within the normal abilities of the NPCs assigned to the
case.
- Do not offer the devices for sale, and put them in the hands of those
who should have them. What happens after that is Story, not Problem.
- If they demonstrate to violent people that light sabres are cool and
they get a reputation for using them effectively, they should come to
expect reasonable counter-measures from the groups who hunt them
(Boba Fett's wrist grappling hook attack) and for the devices to be
looted if they get captured.
If you are not the GM then your options are more limited. If you want to play a by the book Jedi, and you are outclassed by the other characters the traditional approach is to just suck it up (Watch Luke get his butt handed to him by life, the universe and everything in Empire) until they finally get in tune with the living Force. If this does not sound like fun (being the slow starter with a big finish is not everyone's cup of Jawa Juice) then you are really asking yourself if the fun of the game outweighs the frustrations. If no, then don't play. If you are gaming at a con as you say, there is a lot of other stuff to do with fewer hassles.
Closing Music (In this case, the Sandcrawler theme)
In a certain sense, if the group is wanting to build a Star Wars saga of their own, with you in the GM's seat, you have an equal right to contribute to the saga which unfolds as they do. Sometimes that means saying "No" and sometimes that means making compromises. In any event, fun is the name of the game. Star Wars came to us as 'A New Hope' so it doesn't do to let it get you down~
If you are a fellow traveler on a wild ride in a galaxy, far, far away then try to connect with them and appeal to the sense of shared fun. If that fails, consider other options.
but how would performing these almost surely evil acts affect how my character is expected to play the game from then on?
To me this is the most important thing you asked. The answer is: Not At All.
Your character appears to have a well-defined backstory and personalty. Those things define how your character should act. Alignment should reflect those, and that's all. Your alignment changing because of your actions should NOT affect how your character acts, as the alignment just shifted to reflect what you were already doing.
Don't fall into the trap of going "oh I got revenge and the DM made me evil, so now I'm throwing out my character's persona and going supervillan."
Alignment is there to help people who don't have a clear personality for characters, provide game mechanics for things like Smite Evil, and provide some restrictions that we could probably do without. It's not there to act as a straightjacket on what is a well-developed character.
Now, the actual act of getting revenge and fallout from that might cause your character to behave differently. That's RP and entirely in-bounds. If the party treats you differently afterwards that is going to have an effect, but the alignment system doesn't reflect that very well. (Parties can shun good aligned people too.)
How much should other players be aware of my plans?
Depends on the players, really. Are they players who will be okay with some manipulation and secrecy? Or are they players who really value team cohesion and won't appreciate being led around for a secret potentially evil plan?
There's not a good way for me to answer that, as you know them better than I do. I would say that your character probably won't tell them more than necessary unless he's sure that telling them would make them more willing to help.
How careful should I be about players' reactions to having my PC manipulate other PCs?
Same thing as above, really. Some players would have no problem with it at all, others would be rather unhappy.
If my character does manage to enact his revenge (and he may never finish doing so), assuming the actions are metaphysically evil (e.g., knowingly killing a good-aligned entity, etc.), does this make my character evil? What about the other PCs - are they evil? If not, do they turn on me?
While killing a Good creature like an Angel could be called an outright evil act, one evil act doesn't necessarily make you evil. Mortals almost never follow alignments perfectly, they're a mix of different acts and it's more the trend that determines it.
The other PCs may or may not have their own alignment trouble, depending on the situation. How much do they know about why they're helping you? How good are they usually?
And no, if they're helping you do this knowingly and your alignment shifts because of it, they shouldn't just automatically turn on you. That wouldn't make sense, would it?
Best Answer
The short answer is: you need to work with your Jedi player and find a way to remove his character from the party, so he can bring in a different character that will be a better fit.
This party is, in-world, unviable
The longer answer is: the problem you're having is that there's no reason for these characters to be traveling together. The characters shouldn't like each other, they shouldn't support each other, they shouldn't cooperate. The Jedi character should have long since left the group to find better allies. Failing to do this is probably bad roleplaying.
You should start by contacting the player in private and suggesting that he switch characters. Then, you work with him to come up with a reason why his character would leave the group. Maybe he's called back to the Order -- he left, but they still want him. Maybe one of his family or friends needs his help, but obviously he doesn't want to involve the Sith in that, so he has to split from the group to help them. Maybe he encounters a side quest where he can do something valuable or good, but it's a one-person mission.
Once his old character is gone, he can bring in a new character, ideally with the same amount of experience so he doesn't feel like he's being punished.
For future campaigns, it's a good idea to tell people up front: "Hey, this is a heroic adventure -- no playing evil characters, that's for some other campaign." Or vice versa, if that's what you're into.
You've written that you think your Jedi player is "morally uncomfortable playing a bad PC". This leaves you with fewer options unfortunately. You could try to get the entire rest of your group to change, but that's probably even harder than getting your Jedi player to change.
I do recommend offering him the option to switch characters, even if you don't think he'll take it. I personally am uncomfortable playing evil characters, but there's been at least one time when I found myself in an evil group and I decided I'd prefer switching to an evil character, rather than badly roleplaying my good character or leaving the game.
If he doesn't take it, one other option you have is to change your campaign style so the group has fewer moral decisions to make. Give them some faceless enemies to fight (clone warriors? alien invaders? droids?) and don't bring them near any friendly NPCs who could be killed or tortured.