The check box for AWs and event buildings is a great idea. I'd add premium buildings to that as
@Dhurrin mentioned.
I also like the undo as explained by
@Ashrem. It rolls back only the previous action. That seems like it would work fine if you stay in the city map.If it extends to other aspects of game play, there can be problems. An example would be you delete an AW, fight a battle, then notice you deleted the AW. So you undo the battle then the AW deletion. While that sounds okay-ish, it would lead to being able to undo a battle then fight it differently or just cater it. That's just one example to show the undo comes with a whole raft of problems. Even staying in the city there are problems. Can you undo a spell then place it on the building someone just buffed? Can you 'unplace' a building? Someone may have buffed it after you placed it. There are many subtle unintended consequences with the undo idea which can give someone an advantage or make it very difficult to implement.
So, perhaps, just the check box to prevent deletion of AWs, event buildings and premium buildings is the great idea here.