Why not just make the faces outside of the bounding box?
The visual faces aren't the problem. You're still placing the bounding box which is the brick and two bricks cannot be inside one another.
Wait. I could actually just make everything one brick and make the top half have no collision. Problem solved.
Next problem: The inside ground texture. Two options:
1. Studs that DO NOT rotate towards the sun direction because the studs are a print/texture.
2. Ramp texture or plain color.
I'm thinking of doing 8x, 16x, 32x, 96x, and 128x sized planets.
Edit: Another drawback with these is the fact that the planet texture has to be huge so it isn't pixel mush. This leads to longer load times.