I think this is a really good idea.Will constantly mix up the meta and put players out their comfort zone.

To throw my piece in to the mix. Each team should get around 9 bans on weapons. I think any less and you just use the same stuff and it doesn't affect the game. Each team can discuss what to ban but their bans are hidden from the other team. Both show their bans and any crossover is just bad luck. Bans are for both team as well.

As for what weapons can be banned I feel that depending how higher level you are playing then I think you can start banning the stock. I think if you can ban stock weapons then things become really interesting.

I don't think any weapons should be a default ban. This is because it opens a can of worms of why is this ban and this not. If a weapon is buggy then your team will ban it surely? If they don't they let it through and you get punished for not banning it.