They'd need to push out a lot of air in cold weather to avoid condensation on large areas of cold glass. I've been involved in public displays of reptiles for decades, and although I probably sound negative, I've seen lots of enclosure ideas like this that look great to start with, but end up being management nightmares because of the amount of work required to keep them in tip-top shape. They look OK for a few days or a week, then after a few decent cold days when lots of water runs down the inside of the glass into the base, where it's practically impossible to remove or dry out... Anything that effectively encloses a body of warmed water needs to be able to be easily dismantled for ease of management, especially where occasional large amounts of animal wastes are concerned. One of the things which make snake enclosure bearable to live with in the house id that the wastes usually dry out quickly (if they're not removed immediately), but put a reptile in or over (as in GTPs) a large body of warm water in an enclosed environment, and you quicly end up with poo soup which would need several square metres of effective, mature biofiltration to deal with.
Jamie