Check out Belkar, from the Order of the Stick. A chaotic evil character in a mostly-good-aligned party. See this quote:
Despite his kill-first who-cares-about-asking-questions attitude and lack of party loyalty causing the occasional problem, Belkar has proven to be generally effective as a party member [...] but, with carefully applied threats, the rest of the group have generally been able to keep the halfling under control and they consider him to be one of their own.
Note, though, that the OOTS keeping Belkar around has always been a bit of a stretch for willing suspension of disbelief, allowed mostly for narrative purposes, and often lampshaded by the characters themselves, so it might be a bit of a problem getting the rest of your party behind the idea of sheltering a psycho killer, but if you're fun and over-the-top enough, they might appreciate your dramatic value.
Another option that some might not like is getting explicit buy-in from the players, or at least some you think will be into it. Some might see it as a form of meta-gaming that takes away from the real roleplaying, but others might see it as a social contract that allows the party to play the roles they like and build the narratives they like.
Get A Spokesman
Have someone come to town who wants to speak to a spokesman for the area. You could use a few different things, such as a merchant wanting to speak to someone about setting up trade, or a leader of a nearby tribe who just saw these Elves and wants to negotiate with them, or even a bad guy coming in to issue threats.
No matter what you use, the NPC in question should make it clear that talking to an entire committee is too cumbersome or beneath him (depending on who it is). He is only interested in speaking to a representative who can talk for the entire PC settlement. If they want to deal with the NPC at all, the PCs will have to pick someone to speak for them.
From there, you can let the situation organically grow and see if that turns into a leadership position. If it does, your job is done. If not...
Force The Issue
If you can't coax them, you can act more forcefully. You can try this a couple of different ways:
- Have random attacks start happening with increasing frequency. See if the PCs wind up with a defacto leader organizing them in combat (assuming your LARP has combat, you weren't specific on that). If they do, then you're done.
- If they don't organize themselves, have someone come in from a group that's also being attacked by whatever is attacking them and want to team up to fight against them. That person is going to want to talk to a leader.
- If that doesn't work either, simply have an authority figure come in and appoint someone. Maybe the land they moved into actually belongs to some kingdom but is generally unused. When the king hears some people moved in, he wants them under his authority so he appoints an official of the crown, who becomes the leader.
But Do You Really Want To?
Is this actually a problem for the PCs, or is it just a problem for you? I mean, if they enjoy doing things by committee and the disagreements that come from that, why do you want to force them out of it?
In my experience LARPing, leaders would appear naturally in groups when they were wanted/needed. If one never did, it was usually because the people involved were pretty content not having one, and trying to impose a leader on them was a great way to create resentment. That can be fine itself, if you want them to try to undermine that leader. But it doesn't sound like you want to create more infighting.
In the worst case scenario, this can cross boundaries and turn into out of character hostility. I've seen it happen: the people running a game pick a PC as leader who the other PCs don't think deserves it, and that leadership position comes with some kind of in game power. The next thing you know, rumors are flying about that person being the favorite of someone that runs the game, and that's why they were chosen. That's the kind of stuff that can lead to people quitting a LARP, even if there's no truth to it at all. On this stuff, perception is reality.
It's really best to just run the game and let the leadership issue sort itself out amongst the players. If they start failing to complete plot lines due to disorganization, you can point out that the problem was disorganization and that leadership would help them, but you should leave the actual appointing of leaders up to them whenever possible. When it's the group deciding to follow someone, the group is a lot more likely to accept it.
In the end, they're really the only ones who can make a leadership position work. It doesn't matter how much you want there to be a leader if there is nobody they're willing to follow.
Best Answer
There is nothing inherently wrong with this situation, and it doesn't have to mean that the group of PCs are bound to split at some point because of the clashing alignments. However, allowing such a group of PCs means there are responsibilities on the GM and each of you as players to make this work, and all of the players at the table need to be comfortable with this style of play. From your question it sounds like you might not be, but that doesn't necessarily mean there is a big problem here.
Trust and work with your GM
You don't mention how experienced your GM is. They may know exactly what they are doing and you have nothing to worry about. It sounds like your GM is comfortable with the idea of having a group of PCs with sometimes conflicting motives. The mix of alignments that make up the party pretty much guarantee that inter-PC conflicts are going to happen, and in order for these to mean anything in practice, the GM has to use and play on them to some extent or another.
The responsibilities of the players in these situations
When inter-PC conflict such as this comes up, it is everyones responsibilities to try to ensure there is good reason for the group of PCs to continue working together. So while the GM is playing on the temptations of the PCs with clashing alignments, it is everyone in the groups responsibility to work with whatever comes out of any resulting conflict in a constructive way, creating reasons for the group to stay together.
Out of character conversations can be really important
With this kind of thing it can be really important that everyone is on board with whatever is happening to the PCs. With a group of players who are used to playing together this tends to happen more naturally, as they are used to each others play styles and can often predict how each other are going to react. With a new group of players this is more difficult, and can necessitate a lot more out of character conversation to work through potentially tricky situations in such a way as to ensure that all players are comfortable with the way character development and the story are heading.
It might be worth having a conversation to make sure all players are on board with this type of play
From your description of the situation it sounds like the GM might have missed an important step during the initial sessions in the game. As I've already mentioned, this type of mix of PCs is almost guaranteed to lead to a certain style of campaign if the PCs' alignments are going to mean anything in play, and some players simply don't enjoy that style. What should have happened is that a conversation about this was had to make sure everyone was happy with the idea. If this didn't happen, there is nothing wrong with pausing the game to do so now, as it is entirely possible for (often quite subtle) changes to be made so that the style of gameplay is enjoyed by everyone at the table.