Good solution but hard to implement I think.
No. The only thing this forum gains from signature campaigns is traffic. It will survive without them. The forum probablky loses money because money that would be spent on forum ad slots isn't and is instead paid to users. And it wouldn't be hard to implement a ban at all. Signatures would just be disabled and the problem of sig spammers will be solved instantly. Alternatively, and like I have suggested before, I think all signatures should be removed and people have to pay a substantial fee to get them. If everyone had to pay $500 for one or something then it would severely restrict how many accounts somebody could have whilst pretty much eliminating account farming in the process.