The way I see it, a "rating" system which changes people's rate of pay would increase the level of spam, because it would create the idea that signature campaigns are directly endorsed by the forum, when in fact they're just an accepted part of the free marketplace.
Furthermore, anyone who is suspected of being a spammer should be banned. Period. They shouldn't be given partial pay because they're a spammer... just kicked out.
And I'm fine with the current system that we have though it can be improved but we need a better one unlike this one which the suggestion given contains some flaws.
Managers are the people who accepts participants in their respective campaigns hence they should choose the righteous ones with constructive post and monitor whether their specific participants are post bursting or posting rubbish and should be kicked out from the campaign which is the thing that they are doing now.
Also a lot of campaigns nowadays are not accepting participants with red trust or a certain level of red trust with various reasons.