I doubt that really, basically you'd have to set planets to be like moons in the Novas Universum mod. But the other problems are all valid, in that it would be impossible to colonize anything except the star. The rest is only aesthetic.

Then yes, you could do that. Check out that Novus Universum mod I mentioned. Basically you would just be changing the planets in that mod to look like stars and the moons to look like planets. Of course you will still need something to act as the star analog to act as the center of the "galaxy", perhaps a giant black hole or something?