Is there any way that you can reinforce/brace the floor under the mass, or is there no space at all to work beneath the house? A RMH with multiple masses and a manifold diverter might work. You could have several burns, each warming an individual mass. That would likely give you enough slow radiation sources to warm a larger space.
A rocket stove wouldn't heat the whole house, and would be too heavy for the suspended floor.
Building trombe walls against external bricks might be an option depending on how your home is angled to the sun, and how exposed the bricks are to it.
conventional brick and frame house
"How many licks ..." - I think all of this dog's research starts with these words. Tasty tiny ad:
permaculture bootcamp - learn permaculture through a little hard workhttps://permies.com/wiki/bootcamp