Sorry richie, I don't think so xD The jail is small and nothing major happens, so that is fine. However, in the Freeman World especially, since the whole world is only 5000 x 5000 blocks, flying over the whole area would not take long. This would give Timeless people a HUGE advantage, getting the ability to raid wherever and whenever. This might give more incentive for more people to buy Timeless though...
I agree with constin liu he's right. people should not have /fly command in prison but in freemanworld yes that would give another reson to buy timeless and you could raid anywere
Fly would be way to overpowered. Somebody teleports into your base? No worries, just fly to the roof and out. It would be like PvPFest, you're just wandering in the free would and *whoosh* somebody flies above your head and steals all your Protection IV. Sorry, but Prison just isn't the place to implement the ability to fly.