you can edit planet textures in 1.35 for PC. i actually have a mod that changes the textures for venus, mars, mercury and the moon. however, it is impossible to actually edit the orbits and physical characteristics of the planets because that data is inside the code of the game itself and its something you cant access unless you have the original unity project of the game, which is something that only the game developers have and that for obvious reasons wont release to the public (it contains credit card infos and stuff like that, also doing that would compromise the game to people making pirated versions of the game and edited versions that arent the original one, which would break the stable and original aspect of the game). unfortunately, the mod that i did is no longer available, but you can make it yourself using your own planet textures. it not that hard! maybe later i'll do a thread explaining how...