They look like a good idea.
The only two things to watch (that I can think of) are whether or not they are safe to chew, and for anything sticking out that may poke their eyes (something to watch out for un all twig/straw-built items.
But I'm not trying to be dismissive, it's a rather clever idea
Agree that it just needs to be safe. Otherwise I am sure it is much better ventilated than those plastic hideys. I've replaced the plastic hideys with log houses & small plastic stools for when I want to use hideys outside for their lawn munching time. They just have so much better ventilation.They look like a good idea.
The only two things to watch (that I can think of) are whether or not they are safe to chew, and for anything sticking out that may poke their eyes (something to watch out for un all twig/straw-built items.
But I'm not trying to be dismissive, it's a rather clever idea