So I've been thinking about this since mid-winter, about the idea of putting a Double chamber
oven which is inpired by Ernie and Erica's ''Double chamber cob oven'' into a masonry bell.
The bell would be divided into three floors.
Floor number one is the bottom cleanout area and the non-bypassed chimney exit. In front of the lowest stove pipe opening would be a small cleanout door that would serve as a way to prime the chimney (not pictured). A simple bell made of masonry.
The second floor is basically the oven level with two or four holes made in a support slab, through which the gases would flow downwards. This part of the bell, has it's void filled with uncompressed rockwool.
Thirdly, there is the riser chamber, possibly an insulated bypass exit could be present above the heat riser so the stove could be used in summer. The stove pipe exiting through the roof could also be wrapped in insulation to minimise heat transfer through the building (also not pictured).
The core parts for the oven would be cast dense refractory concrete. I am guessing that it could be done WAY simpler than the drawing with the port à la batch and the fancy secondary air inconel tube.

The whole oven mass would be surrounded by a 2 inch thick layer of ceramic wool, followed by rockwool which would fill all the void of the 2nd level, to further minimize heat transfer from the core, to the masonry.
As I mentionned in the title, this is purely an imaginary thought, a concept of a mix between a ''van den Berg style batch box'' and a ''Double chamber cob oven''. An indoors masonry bell oven that could used in the summer time.. The two doors would be insulated as well, at least for the summer time. Mounted on rather large steel plates, both of which would be removable so we could access the riser and the chimney parts. The steel plates themselves would serve as an immediate heat source (I'm thinking right now that we could have a set of glass doors that would also serve as an additional heat source in the winter).
There could be a third door on the third floor, leading to a white oven.
I'm looking forward to sharing ideas with you all!
Good night.