Well my question is how does one construct a city on an MMorpg, Zone control sure planetside had a good system for that but you were never able to construct your own building in any game i know other then Anarchy Online and that was just for guild stuff it had no other purpose and it was already premade cities.
As for players having an effect on the world sure but i doubt it will be anything severe, someone decides to nuke a city thats player controlled, players inside the city not knowing anything about it or having anything to do with it would all be slaughtered noobs or experienced. Things not being looked at are Fallouts have all been single player so no matter what your not going to have the same Domination thing with just yourself or even a guild of players.
Games like planetside were all out war all the time and factions could control zones but only NPC factions, it was up to the players that joined those specific factions to take territory.
God Bless the Enclave. God Bless America.