Basing this on the "Phoenix fast fire" wood fired pottery kiln design. This is a half-barrel style dome. A door could be put on each side if desired, allowing you to rock a couple pies at once.
The firebox is under the floor, heat and gases enter the cooking chamber through a slot on the other end. Sort of a "gray oven".
The exhaust gases exit through the chimney flue on the opposite end from where they entered.
The door would be covered- either bricked (during warmup) or with a kaowool backed plate. The firebox and chimney design eliminates any door height considerations.
This heats the floor first, but pushing coals to the back would reduce this if necessary. Heat use should be very efficient, though it requires more chimney for draft.
Insulation will be full IFB's (I have hundreds of used light firebricks kicking around)
The under-floor firebox could also be used as a smoker box as well, and more heat can be added at any time without opening the cooking chamber. I could get this design glowing almost white (2300F) with enough chimney- which I may do just on principle
My questions- is dense castable refractory OK for a floor?
Are you normally shooting for a hotter dome than floor?