I'm prepared to get an earbashing for thinking along these lines but here goes
I have an outbuilding, about 2.5mx3m. High roof, watertight, large window. Bricked floor. What would be your opinions on keeping a trio of layers more-or-less permanently in here? It's a larger space than I could spare outdoors, it is secure, I could remove and mesh over the window hole to increase ventilation. To my mind it would be like mucking out a horse's stable, in terms of bedding and poop. I could add plenty of toys, perches, garden trimmings, hidey holes etc...?