Most of the thing i wish are already mentioned, but some are not...
* When getting a new haircut you can't be able to shave your hair long
* Your hair will grow and get longer
* You can get stinky and people will say something about it, so you have to take a shower
* When you get busted you will get in jail
* When you do something not too bad, like crashing at slow speed in a police car or something without resisting you will not get busted, but only get like a ticket you have to pay or something
* Maybe some customiseable things like weapons cars building furniture etc
* No vehicles that are like almost impossible to get (like the infernus and comet that you can only get in a single mission and stevie's car list)
* PLANES AND TANKS FOR CHRIST SAKE!
* Realistic wounding, would be cool if you splat in pieces wehen you fall from very high (bit a werid that you will come in all piece out of the hospital tho)
* Ability to turn back time like 3 minutes when you die (to make the above more realistic)
* Maybe only get into the hospital if you're not fataly wounded
I could post like a million things, but most of them are already posted