No builders required for removing obstacles.
I think that with the upgrade times being long, especially at higher th levels, we should not need a builder for removing obstacles. It also gets annoying when you want to switch to a new base but can’t because of the obstacles and you can’t remove them as all your builders are upgrading. Maybe it can be like removing grass in builder base which requires no builders. I feel like this doesn’t affect progression in any way and can be a good qol feature.