Not an entire city should be PVP free for all for these reasons:
They hold essential resources:
Support Perks
Crafting parts
Vehicles
Quest related.
Free For all PVP makes places Ghosttowns
We can see in the HUB what a difference PVP makes between Klamath and the HUB
My Solution is simple, inside everytown there is a zone either marked in red instead of green, or written in big bold red letters.
This zone is where town control will be conducted.
Some Examples:
For Reno, Golgatha will be where the town's ownership will be decided.
For BH the underground/Mine will be where TC is done
For the HUB The water merchants will be where TC is done
Also instead of TC lockers spawning caps from no where, 10% of all caps traded into the town will be what spawns inside of the lockers, when someone spends caps in the town even for quests, cars or ETC 10% of those caps go poof straight into the box.
This also means the controlling faction has a 10% discount on everything in the town basically, TC lockers will still spawn the same items, just the caps come from somewhere.
This idea is mostly to encourage seeing people in more towns across the wastes, and to promote exploration. This'll lead to better equipped new players, and give TC champions more towns to control. A winning team could even brag about it to encourage recruitment of awestruck spectators.