Builder put inside mines and collectors

I'm Th7 max . Currently all 3 builders are free and only TH is left to upgrade to 8. So i feel guilty when the builders are sleeping. So here's my idea
You can put a builder inside mine , collector or drill. He will work in it and give you resources faster. actually he helps do extraction and all stuff in those. You can put a builder inside economy buildings and he will instantly boost their production rate by 30%. No stacking and max only one builder per building. You can remove him anytime and that building's production rate will fall back to normal.

Nice when you have to wait for resources. Boost will help farmers and those who don't have anything to do for builders currently.

Thnx