I just wanted to share some information that might be useful.
In DayZ everyone knows that when the game crashes and you're in a car, when the game unlocks you can be 1km away from the location or dead, it's like you're part of the world while it's locked.
On the other hand in GTA Online, when the game crashes the world continues and only you remain locked in exactly the same place you were.
I think if you made the singleplayer mode that you ask for so much and redid the online system on top of the sigleplayer it would work much better, each player on their own, without depending on the server, my game with low ping is normal in a car, in 140 of ping it starts to bounce around, if each player were independent the server ping would barely make a difference.