1. a green house is not expensive to build
pvc plans can be found online.
2. there is a great artical out there i think it is on chris anderson's website although i'm not sure.
3. shad cloth can be used as most of the roofing to cool it down
4. in the plans i saw the floor and bottom couple feet of the greenhouse was reinforced with chicken wire to keep out raccoons and other nuisance and potenitally predatorial animals.
5. you can build all the greenhouses you want, it will still be "too hot" for panthers between june-mid sept
6. when it rains, it cannot stay wet in your green house, you must have ventilation and drainage, not an option
7. learn from the experience of others and don't keep panthers that can see each other in close proximity, females will most likely become stressed and gravid with infertile clutches, and males will just be unnescesarily stressed all day trying to reach females...also males seeing males will have conflictual/terriotorial displays which is a huge waste of energy in my opinion.
8. in the winter time you can add plants around your green house to help shelter it from cold temperatures, you will most likely only need supplemental lighting from december to march, at this time you may also want to add a humidifier
9. misting systems are always great, but when dealing with a closed environment or semi closed environment careful attention must be taken to make sure you aren't over doing it, shorter infrequent mistings are my best advice
using raised floors is a very good solution to keep ants and such out in my opinion forklift crates work great if you can find four or so and coat them up with waterproof in an industrial part of town, you can find whole stacks of them in perfect condition.
white is the best color to use for the walls as it is the most reflective color besides metallic which is almost fully reflective, but i wouldn't use that for several reasons, stick with white poly film, easy to clean, waterproof, durable
good luck, do search because several people have already done this