Just a thought I had.

For example, what would've happened if Boone were the Courier?
That's an obvious one. Boone hates the Legion and would gladly support the NCR. He'd be a very loyal black-and-white sort of character, always supporting the NCR and never the Legion. However, Boone enjoys killing Silus, so the Monorail may very well end up blowing up simply because Boone can't keep himself together long enough to get useful information. He may also have a bit of a struggle killing Mr. House out of love for his wife; his wife loved Vegas. Another interesting point is Boone may end up killing Joshua Graham, because Boone simply has absolute zero tolerance for the Legion.
The biggest struggle for him would likely be getting the command to wipe out the Great Khans at Red Rock Canyon. THIS would be the pivotal choice for him where all his ideals collide and he ends up at peace with himself or vengeful. (personally I see him coming out vengeful)

The point of this thread is, which NPC do YOU think would build the best nation for the Mojave (under any flag. House, NCR, Legion or Indy) if they were in the Courier's shoes, with all his power and responsibility? Let's also exclude House and Caesar from this simply because it's obvious what they would do as they're the dictators of their very own factions so their actions are incredibly obvious.

My gut is to say Arcade would build the best nation, but then again the Followers prove to be too idealogical for their own good at times, focusing more on how things should be and then missing the practical consequences of their actions and ideals. Another person that comes to mind is the King, as he's very peaceful like Arcade, but more realistic about the situations at hand. He also holds respect and personal freedom above all, so there are very few people that would end up getting hurt by his choices.