i worked for a window instulation company and my uncle owned the place. well we were slow so we build a huge room on the back of his house to keep his workers busy during the slow time. it wasn't the "4 seasons" brand. it was a custom one. we were a typical commercial glass company. so i'm sure if you call any of them they can build it also. all three walls and roof was glass. we put mostly sliders door walls in so they could be opened up to get some air flow.
as mentioned about the build up, HOLY COW!!! did that room get hot.
ok, here's where i was getting at, there is diffrent types of glass, i mean standard glass... so rather than putting the UVB blocking glass. (sorry i forget the acutall name of it it's been 10 years) you can put other types of glass... i mean anything glass i would imagine would work... as long as it was safty glass on the cealing. (tempered they just heat it really fast, it breaks up like busting a side window of a car small pieces. rahter than large deadly chunks!)
now the less UVB you block out... i'm imagining that it'll be more heat... so the room will be like an oven. so keep this in mind. some ideas we later came up with were installing some kinds of exhaust fans and stuff like that.
now this project would be very expensive and probably more than a "4 seasons" room... but you would get what your looking for. i can sketch up and send you the ruff blue prints of what we built. it was custom and it was more of a great room just added to the back of his house, with cathederal ceilings and all... but it is an option if you really wanted to go with a nice looking "sun room" and get UVB in there for your critters.