Can the asteroid mix be tweaked at have some oxide in the mix as well?

I'm guessing you are looking for calcite, either to send down or use in a stationary platform to produce resources?

I have generally committed to not doing anything to change the planet balance that isn't based on a mod setting, but this seems like the kind of thing that you would only notice if you're looking for it, definitely not going to unbalance anyone's game.

Right now I'm trying to figure out what the expectations/plans are for mods for 2.1 compatibility, so this isn't top of mind, but I will add it to my list - it's a very small tweak and seems like it would only be positive.

ive got space platforms stuck in orbit cos theres only carbon and metallic asteroids in orbit and there out of oxide to make ice to make fuel

OK, I mean, asteroid reprocessing is already built in as a solution for that? Turn some of your carbon and metallic into oxide.