Acebird
I am not saying that smaller BK's should do the same, infact if you read back I am saying that stationary yards a Qx is optional.
Of all the obvious things stated, they are why I think that a Qx is a useful tool but if anyone can put up other ideas I would be pleased to consider them.
If I ran some hives for myself at home they would run as double brood boxes, full depth, and a Qx with supers.