Honestly the best way to customize worlds would be a texture/heightmap system like I've suggested before (and have pretty much always been ignored by the devs...not trying to be pushy honestly but I'd at least appericiate a "that sort of system would take too long/ be too hard to implement so if it will ever happen it'll be much later" type of answer, if that's what the case is.
We apprecciate your suggestions very much, but giving every object in the game its very own texture map is sadly not viable. We do this only for known and actually explored bodies, that have real elevation data.
For everything else we use a system which dynamically blends multiple heightmaps to form a random planetary surface.
It's unlikely that every object will carry its own set of textures, due to limited memory.
However, we'll try to find ways to let you customize objects, perhaps even import your own models.