Dave's point of view:

I am in signature campaigns because I am here anyway and might as well make some money while I post.

With that being said, I can also see the other side at least for me. My posting amounts and quality / length of posts can vary a lot based on what is going on IRL.
Busy at work, I will still try to help people, but you might get shorter replies because I am doing work things.
Other things happening in life and I am posting late at night, will also have shorter posts that are less frequent.

But every Monday I get paid the same per post even though for the last few months I have been posting less and they have been shorter.

Doing something like you said, after X weeks / months are going to drop my rank? Will I go back up after I get some of that stuff called free time and my posts get better?

I can see this also having people screaming abuse because they think their posts are better then user X.

If you did it 100% anonymously it might be better. Nobody knows who is making what. This way they can't / wont compare themselves to other posters.

-Dave