Arxhttp://arxandbeta.com/pickban/
In this design, I've just put together a random system that I'd expect people to build on. Like... talk about the downsides of this method?
Only one I can think of right now is that map votes should be alongside picking your classes, with item bans coming later. If we're rolling with pick/bans as a metagame gig, I'd want to ban certain items in certain maps. Making a situation up on the spot, I wouldn't really care for the pain train in a 5CP map, but an A/D map? Sure, maybe having the opposing demo/soldier get more time into capturing isn't a good idea for you as a defender.
e: actually wait, I know of something else. In my mind, I don't see a reason for having to vote for a team captain, because shouldn't a player just be able to ban one item from the opposing team? It nicely balances itself out, because you can't just outright ban all the items off a single good player.