Akula

I recommend skiping that last layer of sticks. I think it might make it very difficult to separate/remove pups, old corm, etc. in the future.

Removing those rocks and stone is an excellent idea...of course being from Florida I have only read about rocks in books and blogs...haha.

I think I would retain a zone from surface to about 1' 1/2' depth free of sticks, wood, etc. so the roots can move around and grow without being impeded. There is a greater risk from excess moisture causing rot in colder zones especally during the winter and fall months when the plants are not growing so be mindful of that issue. My plants are in slightly elevated beds and they do great so your setup should work taking into account moisture issues and root rot.