Re: Warre - only ever add boxes to the bottom?
To answer your questions, the boxes are added underneath because they are foundationless. Put a foundationless box on top, and bees can have a major job moving into it, unless the hive is very strong and there is a good flow at the time. Yes, it does mean you'll be eating honey that has had brood in the combs.
You could use foundation, in which case boxes could easily be added on top and the hive run like a langstroth. But if you did that, you may as well HAVE a langstroth.
You could also move combs around and put one or two in the new box going on top, to give the bees a "ladder" to the top of the box from where they will start building new combs. But again, moving combs is going against Warre philosophy, and towards langstroth philosophy.
"Thinking Inside The Box"