[narf poit chez BOOM]

Not being able to make additional suns is a balance aspect, otherwise crystaline races would have too much of an advantage and would allow too many sphereworlds in a high-tech, massive start. This is also the reason the sphereworld/ringworld is created in the same position as the sun, to use it up.

And, if you just want to create planets, all you need is an asteriod field and one ship with the right component. Note that the component will be destroyed, also a balance requirement and I think in the Last patch it can only be repaired at a shipyard. Stops empires from mass-producing planets until they have a lot of planet-making ships.