It really would have been nice if we could still buy properties, buy houses, buy & run clubs, factories, yards etc...its a good feeling knowing that you're running around banging people up to get your business started. Making money and having something worth while to spend it all on would have been good.
Having special cars purchased stored in the safe house permanently (something like in vice city & the Limo in the vercetti mansion), picking up daily money from your businesses, bulking up at the gym (T.J really looked the part with muscles and tank top).
Carrying out more high paying jobs such as the bank heist, maybe next time we could rob bullion vans, jack gang deals and grab their money, raid betting shops for serious cash, buy apartments and have to go beat people up for rent, burn properties for insurance scams, kidnap people, stop terrorist attacks at the airport, get busted, go to court and thrown in jail, run the jail for a while then make it back out on the street, have permanent girlfriends, have family and friends, be able to call friends or gang members at anytime like in San Andreas, have proper garages where u can store cars, bikes, boats etc.
Maybe in the next GTA, the main character can start from the top, get taken down (eg, sent to jail, lose everything), come out of prison and work his way back to the top by all means necessary.
Bring back the flying missions, helicopters must stay, rich, middle class & poor clothes must stay, the hood (Ghetto), middle class and high class suburbs must stay, area enforcements must come back, drink drive should stay, the triad wars in GTA3 should come back, the modern cars should stay but cars should handle just a lil bit better, car showrooms should come back, bike showrooms should be included, clothes shops should stay.......what more can u all think of ????