Currently we have problems with sig. campaigns cause immediately after announcements, thread get filled in just a few hours. This way only candidates who get their space in few first pages have better chances for joining campaign. To avoid this, manager of campaigns must lock thread for at least 24h, so everybody have same chances.
Uh, no? When I manage a campaign, I select people based on how their post quality is, and if there's a more people that I'd accept than slots, I accept the people who have better post quality. Can't speak for others, but I'm guessing they do it too.
Locking the thread for 24 hours doesn't really help if the thread was created at 2 AM your time, as no one's going to wake up 5 hours early just to join a signature campaign. Your solution doesn't help, and even if it did, it's hardly a problem.