If you must build a Ring/Sphere world, then I agree that the effort should go toward other things.
However, if you make a map that includes these worlds, they can be prizes to be fought over. The build and storage abilities of these worlds make them more valuable then entire standard systems!
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Gaze upon Taz-in-Space and TREMBLE!
<img src=http://imagemodserver.mine.nu/other/MM/SE4/warning_labels/inuse/taz.jpg alt= - /]
WARNING: Always count fingers after feeding the Tazmanian Devil!