C - I'm a bit flexible on what is acceptable as far as driving goes. I can accept both arcady and realistic driving, as long as it's easy enough to handle (at least when I get used to it), and fun to control. But bad driving mechanics are bad driving mechanics, and since a big part of the game is driving, then it would seriously hurt the game overall. Maybe "ruin" is a bit strong, since there is more to the game than driving, but it would definitely make a great game a lot more annoying than it would have been.
i like arcade and sim driving though id probably prefer arcade in this game. the little ive seen of the driving looks great. but it wouldnt ruin the game for me if the driving sucked, theres to many other aspects that i love in gta games.
C/D: If the driving physics aren't done right it will ruin the game
GTA isn't known for being Gran Turismo. It never had anywhere remotely-near realistic driving physics. I can't imagine GTA V having worse physics than the previous games, and if it's comparable then that is fine. Nobody plays GTA games for their awesome simulation of driving.
I'm not here for friends. I'm here for the truth to the best of my knowledge of it, even if it's not what people want to hear.