How about putting a hoopworld around a sun? And another, while we're at it. Having read about
megastructures I haven't yet come by anything like this, which probably means a) I haven't looked deep enough, or b) it's so ridiculous that nobody has bothered putting it down, or c) neither. Assuming c) and waiting anyone to submit evidence for a) or b), here are some properties and problems of this kind of a world based on a limited grasp on physics.
