I have been "Inspired" by one of the random planet names!! So im making a mod just as AWESOME as the name. This mod will change ammo explosions so bigger weapons like Nukes and Artillery and Bombs leave Dents in the planet. Currently the mod is a work in progress, It can't be used just yet at this point in BETA I have built the mod! I'm just waiting on confirmation on if it will work and how long before it will work if the servers aren't capable of handling this kind of mod yet. When i have confirmation that this kind of mod will work i will post the Mod with install instructions
If its not i'll release the mod If it is then i'll release the mod and it will most probably be a change in the dent scale to be bigger than the original
Decals and dust clouds would probably be better. It might even be possible to paint on the planet surface, as done with factory foundations. I'd leave the CSG system alone. I just foresee memory leaks and impassable terrain. CSG is evil.
I also foresee those sort's of issues you stated, but i think jon has also stated somewhere that he wants asteroids and small planet impacts to whittle away at a planet, slowly turning planets into what i assume would be looking much like a golf ball pitted in dents. So if the engine has the capabilities to do this which it does, i see the engine call in some of the ammo .json files. I'm sure my mod will have minimal impact on the game.