There are Pros and Cons to your idea
low cost of materials
Poor draft, the fire will snuff its self out like an ECB. Fire is a bottom feeder it draws air in at the bottom and releases heat out the top: no air= no fire.
You won't be able to snuff out the fire on a short cook and save fuel for the next cook. Charcoal, ashes and drippings all mixed together will draw damp ruining any remaining fuel and also rust out the bottom of the cooker
Once the grease is mixed with the ash good luck pushing that sludge out of a pipe nipple
I never met a Cow that I didn't like with a little Salt & Pepper! Certified PORK-A-HOLIC