It would be interesting to say the least. He is such a classically black and white 'good guy', it would be easier to push him off the deep end into villainy and shock the viewers than say Nathan, or Niki.
I suppose after a few years, he might have gotten slightly more like Future-Hiro, very jaded and totally obsessed with the timeline to correct past mistakes. Something could happen that would set him off trying to to correct that event (maybe a death or something), but the other Heroes disagree with what he is doing, saying that changing history could lead to things getting worse than they are. Eventually he snaps and turns on them, maybe accidentally killing someone during the final argument, and that sends him over the edge. Bearing in mind that at this current point in the shows history, other than Peter, I would say Hiro is the most powerful of the others, it would be interesting to see him try and go back in time to stop Peter ever truly discovering his powers, and then taking on the rest of the group.