This system can be enforced at a later time (after fair warning is given) by having several DT users place a red tag on the profiles of signature campaign managers who do not adhere to this new policy. It can be removed at a later time, but it may be an easy way to identify which campaign managers obviously don't give a shit about the level of quality of the campaign's participants' posts.
Yes, this is a bit of work to enforce, but it's a hell of a lot less than trying to monitor URL types from any given user's signature.
The merit system already addresses the member incentives underlying signature spam. I think a bigger problem is the "minimum post" requirements that campaigns have. I think requiring a minimum of 25-30+ posts per week absolutely incentivizes spam. Managers like it because it makes post counting easier (no need to thoroughly check posts to determine exact number of qualifying posts). Advertisers like it because they are guaranteed a minimum number of spots that will likely be exceeded.
But the forum staff should dislike it because it turns people into spammers. I see otherwise good posters padding their post counts to reach their minimums all the time. If it were me, and I already made 25 good posts but was 5 short of my minimum with a deadline approaching? I would churn out some crap to make sure I got paid. I wouldn't do that in a pay-per-post campaign because struggling to produce shitty content isn't worth upping my pay 17%. It
is worth it if I lose 100% of my pay for not reaching the minimum.
It creates a situation where the problem is not only spammers, but the fact that most campaign managers are exacerbating the problem rather than reigning it in. Props to Chipmixer, Coinroll, YOLOdice and others who aren't part of the problem.