I don't see why it would not work. I have often thought about taking the evaporator out of a college dorm fridge and putting it into a terrarium.
Although in the winter time you have all that sub zero air outside. Gotta be a way to utilize that. Maybe a small vent tube with a fan inside to pipe some cold air to the terrarium, along with the humidifier to moisten it up before it hits the plants. The trick I think will be to not turn the terrarium into a deep freeze.