You can go in discussion with Rockstar about what kind of mods can be allowed... e.g. Vehicles,Peds,Legit Script mods Cause the only mods that I think they're not okay with are mods that can give you money/rp/cars/godmode etc
I don't know if someone already mentioned it but: More advanced pullover features like in LCPD:FR (e.g. Ask ID and Call in ID)NPC Arrest animation for player as it is way nicer.Arrest peds easier when in foot pursuit (I usually have to kill them because I can't get them to surrender)Instead of random glasses and hats just have the ability to choose what you want.Integrated ANPR and Speed Radar (Is it possible to give automatic tickets to people that drive too hard, like irl)A Stun Gun that doesn't kill (as it's supposed to)