Looks good. I've been running 3-queen hives (one queen at the bottom, with two 5-frame nucs on top) using a very similar method for a few years now. As long as the queens are kept apart and each colony has it's own entrance in separate directions, things should be ok. With my set-up (only one brood box) I've found that swarming is more-or-less eliminated - presumably due to an increased level of Q pheromone ?
You might want to give some thought to how you will check for, and remove honey as it's capped - which is not something I have to worry about (I wish ...), and also how you will go about splitting the stack at some time in the future. With nucs, I just pull 'em off and set them on their own stands - your set-up may be slightly more involved. It'll certainly be heavier ...
Very best of luck.
LJ