Exactly, actually. Ball pythons live in old termite burrows, and therefore tubs suit their environments with extreme similarities!
Same with GTPs, just put a few branches in and you're good to go.
If you're so anti-cage/tubs then why do you have so many animals that you keep in cages and tubs yourself? Because that's what works, and it's shown a high success rate with breeding and having healthy animals. They like the smaller spaces, and they do somewhat replicate their home environments.