I can see how a map system would work, perhaps with random player/player encounters (kinda lol if you're traveling into a party though - 1v10, would be kool if high survival skill would give you (or maybe also your team) the benefit).
But arn't there other options?
In Fallout 2 you could get a car, but having a server with say 1000 people and everyone racing around in cars, that's just going to look silly, although if you could upgrade cars and apply guns whatnot to it (Mad Max - gota love it) that could actually make a cool PvP aspect, also I've never really seen a parking lot, so, where would you leave your car?
Or maybe make XX nr of cars, accesible to everyone but the cost to use the car is XX nr of some rare object and once you've traveled and are out of this resource someone else will probably steal the car you left behind and travel somewhere else with it. Or maybe it get's stolen if you make a quick stop to go to the toilet, hehe that'd be funny. It would definitively be fun if you're walking around in the middle of no where and you suddenly find a car that has run out of gas. Use a little bit of science, refuel, vrruuuummmm.
(How do you fit a Super Mutant in a car though... maybe on the roof, with a little wire attached to the steering wheel and a broom to throttle).
What about vertibirds? Isn't that a viable transport option, even though the lore has limited it's use to the enclave. (Or, better said, they are the only ones that have acces to them, even though you did steal the plans for the Brotherhood in F2 (or didn't you?)).
Although I must admit I do would like to ride a Brahim someday and if anyone would want to ride with me, you could ride the other head. Frank "Not even cockroaches kill their own species Fred".
Fred "Well Frank, Cockroaches can't carry guns, now can they".