Since bricks can only be a 64x cube in size why not split the planet brick up? Let's say instead of being one brick it was multiple. 4
3, 16 bricks for the bottom, 24 bricks for the middle layers, and 16 more for the top. 56 bricks in total. The bottom is solid but the top parts are hollow zones so people can build in it. The outside is one solid color print so people can color the inside what ever. Here is an example with mod terrain:
See how the upper edges should have no thickness? The bricks should be made like this but round.
This could also work on 2
3 of 8 bricks and 3
3 scale of 26 bricks. In total for the planets there should be the following:
16x planet (for mini-empires I guess) 1 brick
32x planet 1 brick
64x planet 1 brick
128x planet 8 bricks
192x planet 26 bricks
256x planet 56 bricks
In total 93 bricks, 16x-64x can share textures but above that it should be more specialized. It should probably be it's own category in bricks and not under baseplates.