Start your planet with six pyramidal partitions (imagine taking six \"great pyramids of Giza\", coating all the top surfaces in wax, and then assembling them into a cube so all the apexes are in the center, and all the four sided surfaces are on the outside. Now imagine all the wax becomes unbreakable \"planet core\" block, and all the pyramid stone becomes minerals and soil, except,optionally, an inner cube of Deadly Lava! (tm). Let gravity pull in a linear fashion just like you have it now. Set the volume of the gravitational field as another pyramid coinciding with the soil area of the corresponding side, but with the \"base\" of the pyramid extending to atmospheric height.
Voila! One 3d world renderable in current engine with only slight modifications to gravity, no tesseracts, distortions, illusions or extra client modes. No more mining worlds from the comfort of your ship by hovering under their bottoms. It\'s even cubical and fits nicely into the aesthetic of the game.
The down side is that the skeleton of a totally mined out planet will look a bit like a radar reflector left floating in space. Even that could be fixed, and you might like the idea for the fix anyway. Any planet that looses 75% of its mass could be removed from the game, and replaced with an asteroid sector as the planet breaks up.