One of the advantages I hear regarding the two queen tower hive configuration is that you can inspect the brood nest without having to remove the supers. With the brood boxes placed next to each other, the supers cover five of the frames in each brood box. Those frames covered by the supers could contain brood which would be hard to inspect.
I would like advice on my modification. What if the brood boxes were separated from each other so that the supers only covered two brood frames instead of five? It is less likely the queen would lay eggs in these end frames.
The space between the brood boxes and below the bottom super can either be covered up or you can build a landing board under the bottom super so bees can access the tower of supers without having to enter through the bottom boards under each of the brood boxes.
Thoughts?
Also, if the brood boxes are further apart, is a queen excluder needed?