I personally think the gateway between Blueside and redside is to wide open. as a hero, yes, it's easy to become a villain, you just start being bad. but for a villain to start being a hero... it takes a LOT of work. as far as in game goes i think for a villain to gain access to blueside, it should be a series of story-arcs that you have to complete. The whole process should take several hours if not a couple of days. Doing this would add weight to the decision to switch sides.
But that's just my opinion.