Originally posted by Alneyan: You should be able to build the star where you wish it to be, and you would be able to build a ringworld/sphere world over this star while converting the asteroids into actual planets.
Auggg! Convert all asteroids into planets first, THEN build the ringworld, you can't convert asteroids without a real star.
I got a nasty reminder of this fact once. I was a crystaline race and I was staying in one system. I used the crystaline resource generators on every planet, then I built a ringword, and suddenly had no income. D'oh!
*Coughs* Obviously, who said a ringworld serves as a star for planet creation purposes? Oh, wait, that was me. I guess it says a lot about my *Ahem* love for Ringworlds. Thanks for correcting me on this matter!