Interesting idea matt. However i think the main problem you have here is that in order to fill the cooking chamber with smoke it will also fill the tube your smoke is coming from to. When it pushes smoke down far enough to get out of the exhaust at the bottom the smoke from the inlet tube would be down far enough to choke out the fire. Plus this would be too much smoke probably imo. Another idea of similar nature that might work, is to build a uds as usual but cut an exhaust valve just below your bottom cooking grate. This would fill the top end with lots of smoke and allow it to escape without getting low enough to choke out the fire. But once again the excess heavy smoke might be to much on the food.?
Not to say it wouldnt work just need lots of forethought in engineering. With what i said above your oulet not forcing too much smoke back up your inlet, choking out your fire, and getting a good even heat into the inner barrel.
Which commercial cabinet smoker are you refering to, would love to see a diagram of their workings?
Weber performer, Smokey joe, Weber go anywhere. Mini-wsm, WSM-Soon