Regarding the thermal mass of the hot tub in the small picnic shelter/spa sleeping shelter.
Yes, it will have an enormous amount of thermal mass for such a small structure since it's being built in the style of a breadbox solar water heater. The thermal mass to volume ratio is somewhere around 3 to1 as compared to cob. And of course with water there is little lag time in moving heat to the edges of the container since convective flow will do that whether you want it to or not. Then there's the thermal mass of all the firewood.
Regarding a dehydrating room and smoker in the giant household unit.
Yes, I plan to build a good-sized room which can be used for dehydrating vegetables and fruit but that won't be it's primary function. This will be an approximately 8 x 8 vault type room made from cob. It will be set up as a dry sauna since this is all part of a heating system/spa area. But there will also be foldable racks which allow it to become a dehydrating room and a clothes dryer. Any hot space such as this will dry clothing quite well if airflow is induced. I will configure the exhaust fan function of the mass heater so that air is drawn from the top of the dome shaped roof. Since this will be almost like a separate little building I'll probably style it to look like a Roman vault Temple. This room will not have its own heat source but will instead be molded into the mass heater and it will form the tallest portion of the Trombe wall. The doorway will face south toward the indoor swimming pond and aquaponics area. There's a big structure in Washington DC containing a statue of Lincoln. It looks over a water feature. I'm not going to try to copy it but I'm sure that visitors sitting inside the dome will look just as regal

. I may give the entire interior of this structure a half-inch coating of ferro cement. This would allow it to be blasted with a hose for cleaning purposes. If it starts to smell like swimmers or fish I'll mix mint or some other herb with the wash water. Minty fresh. The only temperature control will be the door and a few adjustable vents. I envision it's everyday usage will be as a spot for swimmers to take a rest and to warm up. There will be times when it simply functions as part of the Trombe wall.
I don't like smoked meats or rather I refused to develop a taste for them because of the carcinogenic qualities so this will not be a smoker.
What will this all cost?
I expect to spend less than $1000 on parts for this elaborate contraption. It's more likely that I will make money in the process of procuring supplies since most will come from demolition projects. I've already accumulated six cast-iron clean out doors, 10 sections of clay flue, and at any time I can choose to save tons of firebrick which commonly goes as fill since few of my customers want it.
Undoubtedly it will consume plenty of labor. But since I'm building a house far larger than what is required for my own needs, I'll recruit helpers who wish to stay in the house for a few months. People pay good money to attend workshops for this sort of thing so it shouldn't be too hard to locate a novice cob builder who wants experience and a roof over their head. This structure will be something that would feature strongly in their resume should they decide to turn pro. I can imagine the whole thing consuming $10,000 worth of labor. That's about what I would expect to pay for a decent oil furnace and the accompanying ductwork. So although this may be the world's most expensive rocket mass heater it will actually be quite inexpensive when you consider the multitude of functions.
When I added 11,000 ft.² to my ex-wife's home 14 years ago it cost me nine dollars per square foot including labor. That was for a house which was sitting on pilings and simply needed extra bedrooms, bathroom, living room and rec room built beneath an existing home, so there was no roof or foundation cost. This time around I expect to spend between $30 and $50 per square foot for a far superior building. This will be a massive savings over the $200 per square foot general cost of building in my area so I think I'll be okay to splurge on the heating system/spa. I'll post cost figures as I proceed and will include $30 per hour for my own time and $12 per hour for unskilled laborers so that everyone can have a realistic picture of the costs involved. I hate it when people understate the cost of things by pretending that labor has no value. So any time that I post the cost of anything done to the property it will include an estimate of hours spent and the approximate value of that work. I'll also include an approximate value of any resources harvested from the land.