I must say, this looks absolutely incredibl
e. A couple of things:
The characters are a bit difficult to discern from the background.
I'd really like to see larger stages (if that is, in fact, the size of one entire stage) whereupon scrolling occurs and whatnot.
The archer should have
aim, not just shoot in front of him.
I really, really, really, like all the ideas that you have for the classes.
As for the Brave, I think that making him similar to the heavy in tf2 would work well, give him lots of health; a strong, general weapon; however, rather than slow him down, give him normal speed. Perhaps even give him a more unique look, if he looks cool, people will want to play him.
How are you going to implement a naming system? Will you have the usernames over the characters, or what? Personally, I think that this would further fill up an already crowded space, however, if you had each user enter a three letter initial, it might fix the space thing.
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I also has an idea:
What if you were in encouraged to play with the same people all of the time, so that you really felt like you had 'tribes'. The more that your tribe won, the further up the overall scoreboard thing you would move. However, the scoreboard is not a scoreboard, it's a map that shows land owned by tribes. The goal is to gain as much land as you can, and if you own all the land in the game.. something exciting happens.
Like so:

Each circle represents a major area, each square being a stage attached to that area. With each game you play, you either win or lose a stage, and therefore stand the chance of losing an area, and finally your total annihilation, whereupon you have to start from the bottom of the ladder again.
These aren't a per-game thing, each server has it's leaderboard (which is in the form of aforesaid map type thing) and each game that you play is on one of the stages of an area. You win stages > win areas > win map > pwn server > get destroyed by some other awesome tribe > go back to the bottom of the map.
I dunno, it's an idea no doubt filled with holes, but tis a suggestion nonetheless.