I like OgNasty's proposal, although I do agree with others that 2BTC is a fairly high barrier. With my current sig campaign, that would take me 20 months to earn. I think something between 0.75 to 1BTC is more reasonable and more attainable.

I also think that we need to be harsher on campaign managers to enforce their rules more strictly and have stricter rules about spam. I think that punishing managers for their campaigners' spammy behavior would be a good incentive to get them to be stricter. Perhaps giving out bans to managers if their campaigners are being spammy and nothing is done about them after they are informed of spammers.