The point in him fighting at 170 is that is where he is comfortable fighting. There are plenty of ways of booking fights so that he doesn't derail a upcoming challenger having him fight Condit coming of a title fight loss is a perfect example. You don;t seem to get that all the MW's cut weight as well and most of them are cutting from higher then 200lbs why does Rory need to fight bigger guys at this point in his career? because he was bigger then Penn?
As others have mentioned Rory is still a ways off a tittle shot with current circumstances he has no top ten wins and it is no guarantee that he beats Condit in a rematch. Worry about him fighting for a title or not fighting for one when he even gets to that point.