Having a large cage is a pain in the butt to clean, I've only kept the balls in the 2x2x1 boaphiles because that's what I had off hand, but I'm definitely considering going to a rack system because of the reasons you stated. I think my girlfriend will be happy to hear that naturally they like smaller spaces, I hope she goes for it. I actually needed to move on of the baby balls into a tub last night and her baby is the bumblebee we have and when I mentioned I need to move one of them and she says "you aren't downsizing my baby!!" haha so maybe my snakes will move into a rack system and hers can keep the 2x2's
Tell her she can keep anything she wants in the 2x2s as long as she's cleaning them. Since BPs are mostly terrestrial, the floor space of the tub is what matters. Most cages have wasted headspace relative to what BPs need.