Skin it with marlite... the thin fibreglass/plastic sheeting you see in walk in coolers, kitchens, and restrooms everywhere. Youll need a furnace blower and a water panel that goes on furnace ductwork for whole house humidity purpose. But in a confined space it would work... insulating it properly would be the hardest part i think.

A basic handful of hvac controls would be a start. Ranco controls is a good brand used widely across the pet trade for temp/humidistats. Most wire up 110 like a switch, just add an outlet.