This gives me ideas:
Limit dualwielding to Gunslinger only.
Limit pipebombs to Demolitions only.
Limit some form of shield to Berserker only. (A spiked shield you can block with, killing Crawlers when they jump at it? >:])
Limit droppable "ammo boxes" for Support only.
etc
Another idea regarding Gunslingers perk powers:
As you all know, most perks have a bonus which is "general" and applies to all weapons.
Like, Sharpie gets headshot bonus, Commando gets reload bonus and so on. Why not make the Gunslinger's general bonus be RECOIL bonus? No matter what weapon he uses, he has less recoil with it. This could be explained by the fact that he uses weapons so much, particularly dual wielding pistols (dualwielding is highly "recoil-us") that he knows how to counter recoil well

Just a thought!