My first thought is that I would be scared of one of the following: If the inner does not have water can it handle water pressure from the outer tank pushing in instead of out as designed?
Would heaviness only along the outside edges of the outer tank cause cracking of the floor of that tank?

I also agree it sounds like a lot of glass to clean. But could be neat, I like the fast flow around the outer ring idea, you could do a stream set up as a kind of loop. What tank sizes are you thinking?