All of what you're suggesting has been proposed in the past, but at this point I'd rather just keep them quarantined in the off topic section than them infecting any where else as you'll just get them shitposting wherever is easiest for them and they'll move from board to board until there's none left. The problem again comes down to shoddy signature campaign managers who don't really care where someone is posting or about the quality of those posts. If people are abusing the off topic section or anywhere else and there's specific campaigns that are paying them for this then they should be dealt with. People can make decent posts in there but the whole reason it's become a cesspool is because of the few campaigns that are allowing themselves to be abused so they should be dealt with if they're causing a problem.
Shitposters will move around, and try to do anything they are capable of (making funny posts, pseudo-good posts) to earn a single merit to become Junior Members. They will try to do this (with their low-quality posts) as their 'efforts' to earn extra money with Junior Member rank if they fortunately make someone laugh and send them a single merit.
Sometimes, we see 'pseudo'-good / -constructive posts from ones who usually or mostly make bounty report posts, but then jump to Meta and make something looks like constructive. Those shitposters are easily to realize by looking at their post history, the ratio between non-bounty report posts and bounty-report posts.
I do hope that users together will help the forum (to be clean, and wipe out shitposts) and themselves because if they won't change significantly, theymos might bring the forum back to what it is years ago. The completely pure forum, without signature.
From what we saw theymos does, when he does something, he usually does it hard. He also openned odds to disable all signature with announcement of merit system and some posts inside that thread. If he does that serious change, he might do it without pre-announcement.
The forum and good users don't have to tolerate shitposts from bad users.
- Removing signatures or sig ads globally.
I very much do not want to destroy the sig-ad/airdrop/bounty "industry". But I am not going to tolerate people posting garbage upon garbage. If the merit system completely fails and I can't think of anything else to replace it, then my next step will probably be to completely remove all ways for forum users to make money from posting (eg. removing signatures entirely).