I agree - excellent cage for a single dwarf. You've set me thinking about putting Bean in ours now instead of a Rex.
If you are clever with the tubes you can make an underground tunnel for your robo
The one thing I don't like about is the water bottle - it's too big and, if you remove it and use a different one, you've got this hole in the roof. That's really why I've not used it so far, don't know if you can think of a way round that?