The only problem i can think of is that if the animal is in anyway stressed or maybe if there is any trouble between hosue mates you might end up having one sitting at the top all the time, where there would be very little heat. Can you find tubs which arent as high? Plus I could imagien it being a bit tricky to get the animals out if they are at the bottom, even if you make the top floor removable, as it would mean a lot of moving about in the enclosure.
I keep leopard geckos and g. luii in plastic containers, but they arent particularly high, and look a little wider / longer than the ones in that pictures, and they work very well. I am having a lot of luck with breeding both species in both, and they are very easy to keep at the right temperatures.