I'm trying to visualize the process you are trying for,so I'll toss out a couple of thoughts.
Direct cooking over charcoal/wood, will burn up the meat drippings,as they hit the hot coals,etc.
This adds another aroma,and possibly a flavor element.
The traditional Cookshacks have an oven heating element,much as your home oven,in the bottom.
It cycles on to peak heat,until the set oven temp is reached,and then it cycles off.
This repeats,throughout the cooking process,just as your home electric oven does.
The perforated wood box encloses the element, allows the wood to rest over the redhot element,without the ash covering the element.
The wood will burn,become charcoal,and then usually become hot ash.
The wood product will not only provide the smoke,but gives some carryover heat to the wood box,between cyles of the electric element.
The top /roof of the wood box will vaporize liquid,as it hits.
Now ,depending how much sugars,etc. may be in the drippings,accounts for all the "gunk" that winds up on the foil,after the cooks.
The grease,that is in the air in the cooker,may settle onto the roof foil,or the foil on the floor,and flow into the grease pan-much as in most other types of cookers.
I'm no expert,but this is how I visualize the process from my cookers.
The commercial smokers are NSF, UL, ULC, USDA so this should satisfy the governing bodies.
Hope this helps a little,and give me a shout if there is an area that I might attempt to clarify.