good idea for reducing spammers but main goal of signature campaign is maximum exposure
and seasoned bounty managers already have their own ways to sort out spammers

I would think limiting participants on bounty and signature campaign might be an option
managers should allow a user to participate only on one category: (social media) bounties or signature campaign
if such things enforced, we might see less bounty hunters spammer trying to rank up for better sig camp pay rate

so each user would be compelled to choose path as social media specialist or forum signature specialist
social media specialist (bounty hunters) doesn't need forum rank and activity to apply
their social media specs: friends, followers, etc will be used to gauge their capabilities

this probably creates new issue of multiple accounts, 1 real user creates 2 accounts for each purpose