How will the thin steel drums react at 1700f? My guess is the inside one will warp for sure.
You won't have the refractory properties of the exposed ceramic dome and side walls which I think are key to the cooking of an egg.
The dome shape is key but the hinge will be a big project. How about a side door instead of an opening dome?
Air flow around the charcoal and out the top center of the dome are key as well. You'll need both of these to get it grilling hot. The ash will need a big place to drop out and not effect airflow. The bottom grate in a BGE is cast iron to take the heat. I think expanded metal will have a short life.
Keep us informed.
The Honey Badger of BBQ. I just don't give a sh!t.