I think Paradox, or Professor Retcon as I've called him, could have been an interesting character but it seemed to me that he was there not to expand the Ben 10 universe (or multiverse) but to narrow it.
Fans suggested the idea of multiple realities as a way to deal with continuity errors and allow for stories that take things in a different direction.
It seems that CN tried to pour cold water on that with paradox and his idea of a "Prime" timeline. The others are just off shoots and of less importance than the prime. (The lives in those timelines are less important to I suppose.) With this they were saying that there is only one Ben 10 and this is it. Don't like it...don't watch.
Even when they showed other timelines they really didn't get very creative with it. I could name several ideas of interesting alternate versions of Ben 10 that fans might enjoy.
I think he could have worked if he were done in a different way. Perhaps he was a time traveler lost in the stream of time (Not too far from canon) and he now travels the multiverse trying to get to his own reality, (Somewhat like Sam Beckett from "Quantum Leap")