Guilds
Guilds are something that goes hand-in-hand with a MMO, but Eve makes the guilds matter. Eve allows the players to make giant corporations, essentially your own army if you try hard enough, and that is something that Project V13 should definitely make sure to take from them. We would love to generate our own group to revolutionize the town we're in, or to destroy the town, that should all be an option to the players. Start a trade group or a mercenary squad, start some real estate or conquer the estate, the ways players can make it go would be endless and peoples Role-Playing would be there like no tomorrow. DO NOT follow WoW, I don't care how famous it is but when you have two opposing forces that can't take each other's land or fight against the other for any cause, that eliminates the RP from the game.
The Map
Eve is massive, and allows everyone to be online but in different places. Project V13 needs to have more then just one territory, by that I mean more then what New Vegas has currently. Project V13 shouldn't just have one large area, but multiple locations that don't even need to be connected but can still intertwine with each other. This allows trade to go not just from town to town but state to state and possibly even internationally, development of one area could harm or benefit another or do nothing. One military could decide to march through all the areas, alliances could be formed, and the story and freedom will be all the more recognized.
As I said, Eve is the MMO to follow for the Fallout Universe. Fallout has been based of a story of chaos and reconstruction that we all want to be a part of, but we don't want to be doing the same stupid quests over and over again, we want to make our own quests, we want to develop our own world in the Fallout Universe.