1. Do we think there will be that many that apply for this ?
That was my first point. There will be no one applying at the 0.5 BTC price. When a new Copper account costs $10-20 you're basically placing a $2000 penalty on honesty - if someone wants to evade a ban they'll just create a new account, and if someone wants to play by the rules then it's way too expensive. For it to make sense it has to cost about as much as Copper membership give or take a few bucks, if you consider sentimental value vs loss of signature vs ban evasion.
2. The work you do now would be paid in theory ( i know you don't care about that) but others might start helping with financial incentive. This also provides incentive to the mods to escrow and the reporters to keep any eye out for sig ban evaders. I think if anything you will get more people looking for bad guys and watching they stay in line if they are paid from the fees.
3. after the get to go back to normal then they will just get caught again and their usernames will be on the thread prior so go to insta perm ban.
It's still a lot of hassle for zero benefit for most people involved. I'd rather spend that time cleaning out 100 other shitposters than babysitting one ex-convict.