OK, so what you do is to build a hollow sphere the size of the
Earth. Make the shell of whatever works best (probably doesn't have
to be diamondoid), maybe 1 000 metres thick, with maybe another 1 000
metres or so of dirt, rocks, etc. on top of that. Stuff the whole
thing with Utility Fog (maybe just a layer 10 000 metres thick).
Fill the rest with air. Do not rotate. The UFog pushes people, etc.
against the inner shell (or rather, against the dirt and such).

Heck, you can probably put the UFog right against the shell, and let
it form the rocks, water, and so forth. Even "wildlife" could be
simulated to a high degree of realism. Want dinosaurs? You got
dinosaurs.

But even if the UFog was relatively "stupid," it aught to be able to
do the basic job of "hold everything down."

Xenophile (taking off on a flight of fancy, yes, but still, it seems
doable, given UFog)