A few new ideas i came up with, some can be done, some would be hard to do:
road construction equipment - 'hey, sherrif, how do you stop a bulldozer?'
more realistic vehicle damage - backing into a light pole puts a light pole-shaped dent in the back of the car, not just generic body damage
even more weapons! - did someone say grenade launcher?
car dealerships where you can buy cars and you own them - you can park it somewhere and it won't disappear- unless it gets stolen or towed
modify vehicles - extra armor plating for stuff like the Taxi EX-Missions, etc.
more environment interaction - need a shortcut? blow up a building!
tow trucks - double-park your getaway car and it gets towed away, also the car on the back could be a good weapon against pursuers, and you could tow away vehicles (perhaps a Tow Truck EX-Mission?)
car haulers that can carry cars - enuf said
slow down the game time a little - make it about 3/4 the speed it is now
smarter player-allied gangsters - (the following mocks tommy's gangsters in Vice City) Tommy- "hey, guys! they're shooting at me!" Stupid Gangster- 'huh? we're ten feet away, so it doesn't affect us.' Tommy- "what the **** do i pay you for?!?"
u|\|l0<k 5\/\/337 l3\/\/7 \/\/17h 54\/35 fr0/\/\ 07h3r G74 g4/\/\35!(sorry, lapsed into g4m3r5p33k)(translated, it means: Unlock sweet loot with saves from other GTA games!)- stuff like graphically updated versions of GTA, GTA:London 1969, and GTA 2 with saves from the respective games, and something cool like mixing in the GTA 3 vehicles and unlocking GTA 3's main character to use with a GTA 3 save and mixing in VC cars and unlocking Tommy Vercetti to use with a VC save
* note- by 'mixing in' cars, i mean having GTA 3 vehicles 'replace' 25% of the next GTA game's cars, and VC vehicles would replace another 25% of the next GTA game's cars (so, if you had a GTA3 and VC save on the same memory card as the new GTA game, the car mix would be 50% new designs, 25% GTA3 designs, and 25% VC designs) EXAMPLE: if there is a Cheetah in the next GTA game, and you had both a GTA3 save and a VC save, 50% of the Cheetahs would be the new Cheetah, while 25% would be the GTA3 Cheetah, and 25% would be the VC Cheetah. The old designs would only affect vehicles with the same name, so if there was a vehicle called the Nightsabre, it would remain unaffected, because there isn't a Nightsabre in GTA3 or VC.
** note- by 'unlocking (character)', i mean either: A) unlocking an actual, different digital character, or B) unlocking a different 'skin' for the main character, so it would still be the same character, just with a different appearance (like the cheats they have for GTA3 and VC.
that's about all the paragraphs i have today. enjoy!