I think it would be quite useful and prevent a bit of hassle if the mission exotic, dyson and rifts of people who have reset/been banned just revert to the planet they were pre transformation. This would not only prevent confusion and ppl getting mad over not being able to attack an awesome planet, it will also prevent the wastage of top quality planets such as pre-rifted nat dysons which will not get used and will never be able to get used once a player resets or is banned.

would be nice yes, but existing ones cannot be reverted because their previous information would have been most likely lost(specifically, all info on the exotic, size/res info on the dyson and planet type, size info on the rift).
would be a nice implementation for future planets thou, been suggested many times.

Just remove them from the game, and a new planets in their place.