I think size may matter in the quality control aspects of making charcoal. The bigger the fire pits, the less consistency I seem to get from my charcoal. If you had a way of introducing a controlled amount of oxygen into the chamber, then you would be able to keep the decay process moving so that more of the wood converts without having too much charcoal turn to ash. It is all a balancing act, which is what makes the dutch oven process seem to do better. Smaller batches somewhat isolated from the direct combustion area seem to be most effective.

Given that, yours should be a viable process with substantial recovery still possible after some practice I reckon.