This is unnecessary. We're just complicating things at this point for the sake of being complicated. The time it takes to drive from LSIA to Paleto Bay is really just the time it took you to drive there. Nothing less, nothing more. You're probably taking a different route to another player, so that's going to be a different drive time. I understand the realistic aspect of it, but some things are never gonna work here, because after all, this is just a game.
Imagine the fuss when a bigger roleplaying scenario happens and everyone has to travel the entire map. It's gonna get confusing, don't you think?