SUGGESTION
What if we looked at this another way?
Perhaps, instead of looking at it from the inside, we look at it from the outside.
What i mean is that, it is well known that the popes are extremely powerful, and even history concludes that they were power hungry, that is mainly why there were so many problems between the Pope and the Holy Roman Emperor - and many other problems besides.
What if, there was an radical, power hungry reformist-type like pope who did challenge the catholic faith and the way that it was practiced, and he could have changed it, drew a large following of sorts amongst the clergy and even the catholic followers. He could, in essence, become an anti-pope and create his own catholic faith. In the end though he would have to win out against the current catholic system.
The biggest problem that i foresee (among the many) is to choose which Pope would be better suited to this ideal?