Although I have yet to obtain the game, I think that a jail/prison system would work espeically well with this game in particular sincet here are 3 protagonists. Getting "busted" should actually feel like being imprisoned instead of just spawning outsife of a police station.
I also think it would add to the role that money plays in GTA. Just a little detail I've found rather interesting for quite some time.
What are your thoughts on this sort of feature GTA community?