this although Good, do you have proof this would happen is Lanius went back home? he's a butcher not a thinker.
personally i wouldn't mind seeing legion in another Game BUT in the early days, Josh still legate, a young ceasar etc.
Time travels not possible, nor will they, Bethesda, do it.
Caesar has stated that he has "We have cities of our own, but nothing compared to Vegas..." to me this would mean they have civilized people doing "average Joe" stuff like farming, building and shopkeeping. Crime is nonexistent in their lands because of how well they enforce law there, so maybe there is a tough presence of military guards stationed every few blocks - possible Frumentarii amoung the people reporting any suspicious behaviour to said guards.
I'd say the men who are born into the Legion but aren't fit enough to be soldiers and not too unfit to be killed are given work on building the homelands along with the women.
The people we see in the Fort, I take to be recently enslaved women who are part of NCR or unknown tribes, those born into the Legion are given their place back home but can never serve in the Army.
The Legion have their own currency, coins, so they should have some structure in earning and spending those coins: Earning would be through work on the farms, construction and scavenging useful materials/weapons, and obviously spending it on food/drink and other misc things needed to live, also trading with any caravans who deal with Legion.
It's all assumption until a Dev or someone says otherwise.