I would recommend using the Monster Vault maths, found summarized on Blog of Holding; or, Monster Maker is a handy app that helps create monster cards, and will work out the maths if desired.
Set out which roles you wish the monsters to take - from the sounds of things it seems like you'll have a mix of Lurkers and Skirmishers, with Soldiers and Brutes making up the majority of the rest. Adding some of the other roles (artillery and controller) will help build variety.
Essentially you will be making sets of 'monsters' to form into encounters. From memory approximately the same number of same-level enemies makes a relatively balanced encounter, depending on the level of optimization and experience of the players. Mix and match some monster types, replacing 1 monster with 4 minions of the same level, and nudge up or down to taste.
For example, for 5 level 1 PCs you could then have 2 'Tough Monks' (level 1 Soldiers), 2 Ninja (level 1 Lurker), 4 mook monks (level 1 skirmisher minions) and 4 ninja mooks (4 level 1 artillery minions).
The DMG 2 has a section on making monster 'themes' - in essence by putting together sets of additional abilities that are thematically linked - such as the Goblins' ability to shift. For instance, you could add an ability to the Monks that acts in a manner similar to the Monk PCs flurry of blows - maybe on a successful attack they deal a small amount of damage to an additional adjacent enemy, maybe 2 damage for a level 1 monster.
One of the easiest tricks for 4e is to simply 'reskin' a monster - presenting for example, a goblin or a kobold as a ninja is just a question of description. Find a monster which has the relevant ability (such as shifting on a miss, those pesky goblins!) and you're good to go.
Generally a 4e encounter is much better with some environmental factors, so I'd recommend adding in some interesting terrain features or traps to spice things up a little. Broadly speaking, avoid adding in higher level Soldiers or Brutes too much, because they can become hard to hit leading encounters to bog down. Lots of minions is useful in making an encounter feel exciting and allowing the PCs to feel capable heroes - it all comes down to description when using minions - you can make the heroes feel awesome or like they wasted their attack depending on how you invoke their sense of adventure.
The monks could have the ability to spread some splash damage as a flurry of blows, the ninja should be tricky to pin down, maybe with a teleport style ability or a jump. They could climb walls with normal movement for a more HK film feel. The tattoos sound like a great idea, possibly you could borrow from Legend of the 5 Rings and each style of tattoo grants an ability - so the monks with flame or dragon tattoos can breath fire. Monsters that spawn other monsters are fairly tough - the Wraith in 4e does something similar I think. Make sure that whatever comes afterwards can't spawn more monsters - maybe it generates a minion when killed that lacks the respawn ability. Alternatively, you could describe them as crumbling and rising once they hit Bloodied, with some new abilities?
You choose only one of the options. This isn't actually ambiguous in English—choosing from a lettered list is a convention that always means "or" except when specifically stated that more than one can be chosen.
The ses in the words like arms or defences do not indicate anything to the contrary — that's another feature of English that's potentially confusing, but also unambiguous. In English, the s can mean either a word that's grammatically plural or grammatically categorical. Categoricals are words that indicate represent kind without meaning singular or plural. You would not say “choose your defence” or “choose your arm” — at least, not without being grammatically incorrect. For those uses, the categorical must be used, and the categorical is formed the same as the plural — but does not mean plural.
So the Druid must choose either Hide Armour or a Wooden Shield but not both, and similarly for the other classes with these choices.
Best Answer
The general presumption in most editions of Traveller (including the Mongoose version) is that characters have retired from their careers at the end of character generation and set off to start a new life of freelance adventuring. So the normal thing to do at this point would be to make your mustering out rolls for all careers (including your final career), which should give you some money to purchase equipment, plus perhaps a little free equipment, depending on the benefits rolled.
This doesn't seem to be directly stated anywhere that I could easily find in the Mongoose Traveller 1st edition rulebook, but step 11 of the character creation process in the sidebar on page 5 is the only place which mentions finishing your character, and it presumes that you have left your (final) career before doing so:
If you want to instead run an "in service" campaign, then the GM should assign equipment based on the service you are in and your specialty within that service, but this equipment is owned by your employer, not your personal gear. Note, though, that this approach could prove difficult if your group's characters are not all in the same service (why is a civilian Merchant on the bridge of a Navy ship?), so I wouldn't recommend it for your first Traveller campaign.