I'd like to think that you have taken this idea from a comment you left long time ago on one thread of mine about people who used 100+ accounts to join social media bounty.
As I suggested at the time this is the best way to limit the multiaccount since now with the merit system is almost impossible for one guy has 100+ full members accounts, even if he will has 100 of those accounts we can easly hunt them with a little of effort and red trust them.
Limiting multi accounts is impossible. It's too easy to use a public open VPN, and open an account up. Yeah, the IP will eventually get banned but, they'll then just move onto another clean VPN. They'll then post under Tor Browser, and without some very in depth research it would be difficult to prove who's an alt of who.
Plus, alt accounts have their uses. I personally have an alt account that I access when using insecure connections. Same as Loyce above, and theymos also does the same.
Firstly, I don't get why would bitcoin-based campaign generate less meaningless spam. How does that work?
Secondly, if you don't like the idea of signature campaign and you believe that it'd be better to forbid wearing signatures up until Full Member rank, than why do you keep running all these campaigns and allow "members" to join in?
Requirements are generally higher because, they are run by users that actually care about the forum. Instead, of some random user that is in it for the money, and doesn't care for it at all. Plus, a lot of the bounties in the Altcoin section run campaigns with new accounts.