Hmmmm, what about "pets with benefits." Worms that help compost, bunnies that make poop/fertilizer, even using the poop from your pet bird, fish that you keep that you use the water for watering your plants (or grow plants aquatically from the tank). Maybe angora rabbits--or even dog fur--that you use for spinning or stuffing.
Maybe there could be a BBs for:
- water your plants with the poopy water you sucked up from your fish tank
- harvest and utilize bunny or bird droppings
- harvest fur from your bunny/dog/cat (this might fit better into textiles)
- grow plants in your aquarium (here's a thread on growing food in a tiny aquarium for cheep, and what fish to use, etc
https://permies.com/t/84041/grow-herbs-fish-cheap-Easy)