What would be the problem with letting someone roll back their rushed town hall? Let's say you want to roll back a level. You can pay something, ie 1 million gold, and your TH immediately rolls back one level. You lose, with no refund anything that was at the higher town hall level, and anything that was upgraded to the higher town hall level is downgraded to the max for the lower town hall level.
Example: Rushed TH 9 with one xbow, one level 7 air defense and two level 6 air defense, and a queen. You pay the fee and roll the TH back to TH8, you lose the xbow and queen and you keep three air defenses, but they're all level 6. Trophies and XP levels are unchanged.
This could really help someone who didn't know what they were doing and rushed too fast and want to fix it, to make the game enjoyable again.

