Heya, A friend and I have wanted to start making mods for New Vegas, and I actually suggested this to him today! What I was thinking is that Nipton could be repopulated with some of the NCR refugees that are in Freeside, or just about anyone in Freeside actually. As for the general improvements for Nipton, I'd imagine clearing the area of hostiles (like the Vipers or the scorpions in one of the houses there) would be start, and then creating several towers for defense. As Nipton would still be quite weak, establishing relations with either the NCR (if it wasn't already NCR itself) or the Powder Gangers for extra defense could happen. I honestly wish to make a mod that expands a lot of minor things in the game like the caravans that are up at the Mojave Outpost. I bring this up as the caravans only have two ways to get to New Vegas, and one of them is guarded by Deathclaws, so I'm going to guess and say they would instead go through Nipton. I don't see why Nipton couldn't have a (flavour) tax on caravans to help boost the nascent economy. If anyone wishes to work on this with myself and my friend, hit me up on Skype (neonkartoffel) or gmail (OstDame), Cheers!
