Setting up one tub as you specified is fairly easy. A shallow 32-qt latchbox would be ideal as the lid can be locked down securely, and it gives a decent amount of floor space for a smaller snake.
Since tubs don't retain heat well I would use a UTH that covers 1/2 of the floor space versus 1/3 of it. Covering the tub with a small blanket or a bath towel would help it retain some heat when your house ambient is in the low 70's.
Add matching warm/cool side hides and a water bowl in the center of it, and you should be good to go until the AP enclosures arrive.