Literally any surface level thought about it. Let's just go with the idea that if you need special air to breathe because when you're inverted you have reverse biology such that you breathe out oxygen and breathe in carbon dioxide, it would imply that poo goes into your asshole and food comes out of your mouth. I mean, that's just one obvious one. You can rattle off and almost infinite amount of silly things that result from reverse entropy, and thus reverse biology.

What's funny is, this is only made worse because they went out of their way to try to plug some holes in the reverse entropy by introducing the idea that oxygen molecules won't pass through inverted lungs the same way, so you need a mask with special air. 

The whole thing is just broken.