^It's been tried.
1) We did 15gal batches..........sort of heavy to be lugging through the yard.
2) It is dirty....I mean DIRTY in there. Bug city. Always damp.......drips coming off the ceiling......dust everywhere..........muddy floor.
3) Most importantly, the temperature is MORE stable in there, but not stable enough....or low enough in the summer, to promote a good lager fermentation/aging cycle.