[quote=@Jeddaven]

I think one of my big narrative issues with the legion being 'together' as a single enetity is that it severely limits the ability of people to mess around in Colorado; that'd mean most of Arizona, new Mexico, and large parts of colorado claimed by a single person.
[/quote]

Well, there also gives a counterpoint to be had:

We could have the Legion be an NPC entity that anyone can "write for", and instead have the players themselves play factions within the Legion itself. Same goes for the NCR, since the NCR has tons of factions within it (Followers of the Apocalypse, Gun Runners, Crimson Caravans, OSI, etc.). 

Keep in mind that this is more of a "West Coast" sort of issue, since the East Coast doesn't really have much in the way of super-established factions that would "map paint" most of a region.