"Heat Engine" recommendation request

Hello great people here.
I have been reading some of the topics on permies on and off for awhile, but this is my first post. I live in the mountains and heat our brick house with wood. I'm tired though of all the mess resulting from bringing the wood indoors, and especially the smoke given off by the two metal stoves we currently use, one in each of the rooms we have.
I dream of building a small annex in the back of the house, directly on the outside of the rooms I want heated. I wish to build an efficient, hot burning wood stove there, some sort of rocket stove I imagine, I'm open to suggestions. That would be the heat producing "heat engine".
I wish to pass the hot gases inside the house thru an new opening in the brick wall, where they would heat a thermal mass (bell or bench, not decided yet). The cold gases would exit either thru the existing brick chimney that already exists built into the house structure, or thru another opening in the outside brick wall.
I envision burning wood as needed during the day or afternoon and thereby heating up the thermal mass for the remainder of the evening and night.
The question I have for you is which type of "heat engine" would you recommend?
I wish for something that would be able to burn unattended for longer periods, I'm not too keen on tending the fire every few minutes as some of the J tube rockets seem to require, and I wish to be able to burn both thinner wood/branches but also bigger pieces of split wood, hoping I can insert a larger quantity of wood fuel at a time and leaving it alone for a longer period (minimum 45 minutes or longer if possible). A longer burn time is important to me, if it could be achieved, not necessarily burning all the wood very quickly and releasing lots of heat at once.

I contacted Matt at Walker stoves since I was hoping his design would work, but he pointed out that his burner cores exhaust the hot gases on the entire top surface of the stove, great for a cook top, but not easy to channel into a hole in the wall into the house.
I don't wish for a tall riser though, as I need to channel the hot gases into a bench, I wish for the exhaust to be lower in height.
Looking thru the topics on this forum I see many designs that look potentially very good, but me being new to this, I wish for your recommendation for design that is known to be reliable, fairly easy to build out of fire brick as high tech foamboard might be difficult to source in my country.
I see many designs discussed: shorty, sidewinder, batch rocket, etc, etc. Which design do you recommend I should start studying first, I'm a bit confused and feeling like taking a drink from a fire hydrant at this time. I like tinkering and learning new diy things, but I don't want to make it into a new career, and I wish for something that would work reliably so that other family members would learn to operate easily if I'm not home.
Thank you very much for your suggestions and ideas.