Suggested more times than one can count, and we don’t know if it’ll happen because it’s not exactly easy to implement. If it were to be implemented, terrain would have to be randomly generated, which isn’t easy to do. Otherwise missions would get boring very quickly.
Inner Planetary missions were suggested a lot of times in the past. It’s not confirmed that they will take place in the game in the future. and well. due to how enemies they need and several world generators they need it’s gonna take long to be done.