I like the concept. It appears the cages are based on proper outdoor or indoor ambient temps and humidity levels.
As far as permanent housing, I am not sure if the cages would work in environments where it gets very cold or dry.
I would have concerns adding any type of heating source. Fire hazard issues need to be addressed concerning the materials used for making the cages if they are stating heating sources can be added. Maybe that's been done? I looked at the link and I didn't see information about things of that nature.
I do like the fact you could bring a pet outside in the right conditions and feel fairly confident you could leave it for an hour or two.