No, we can't build a fancy barter town just because of a lack of safe cities, that's no excuse. As said above, there are MANY safe cities in-game, they're just completely abandoned.
The cities in-game weren't designed for an MMO. MMO's cities usually have places to retain the people, to keep them there, depots, warehouses, shops, banks and so on. NCR has those, Hub had some movement before but not so much right now. We must think of ways to attract people to the unoccupied cities, for that we have to think about city design, regional resources, etc. Whatever we can think of to distribute gaming population.
I think that if the devs can't test the scripts, there are huge risks: imagine your game crashing from a script, already implemented, and you end up with a blocked log in or something? Only the devs can know what might happen due to script bugs, I won't even go there. I think we should focus more on making the other cities more attractive to players, and thus giving a meaning to them, rather than building entirely new ones.