Sunspot
Your investing a lot of time and energy to a new system. I would humbly suggest to educate yourself in the low temperature heating methods. One of the best is in-floor heating. There are others with larger surface area, heat exchange surfaces with a small fan force.
The solar hot water panels can be quite effective as we have actual success with our system. One full day of winter sunshine equates 24 hrs of space heating for us. Even at minus 20 Deg. weather. FREE
But without a good method to distribute that lower temp heat this may leave you a little dissatisfied.
The old cast-iron radiators are the old tech. that require very high temp water to offer any sort of comfort. They will work with a wood fired boiler but you will be kept warm with the constant wood cutting hauling and loading of your boiler. I understand you will have a huge heat battery but you will have issues with trying to keep it at temps around the 80Deg.C plus temps.
Growing up my dad installed a Newmack combination wood/oil boiler. Having a home with three strapping boys to help with the wood cutting, splitting, stacking, filling the boiler etc. It worked, but we now know how to do it better. That thing (boiler) only heated the home at a boiler temp 80-100 C deg. Problem baseboard radiators.!!! The convection needed very high temps and it took a lot of wood. All of us really got tired of dealing with wood. (except for one brother "The youngest") He still likes fire!!! We'll see how that will go as he just turned 50 yrs.
If you employ the lower temp methods the solar will work extremely well and the wood boiler can be used as your back-up when the sun isn't around. You will need only a small fire heating the large heat battery to 40-50 Deg.C
Heated floors are amazing. Check out the Uponor product with a nice tile on-top. The niceties for in-floor are it won't occupy any floor space or leave marks up the wall from the convection over a radiator. A beautiful tile floor is the actual functional attribute for heating. The heat is so uniform. The cat will sleep anywhere on the floor in the room and not just next to the rad.
DO NOT EVEN entertain the idea of between the joist heating loops with spreaders.
If you have forced air ductwork installed you could use an oversized air handler on a low speed setting so the house doesn't feel drafty.
The amount of solar collecting area is important. For flat plate (if you planning space heating) Min 10% of your floor space. But to be totally sufficient 20-30%
You had mentioned about your wall space area. The collectors work better vertical for winter heating. Increasing the total area of collector is totally worth changing a window to a long narrow (floor to ceiling) renovation.
Its a lot of work!!!! But, so is cutting wood. I'd just prefer to do it once.!
I can't do the explanation justice, of coming home after work, knocking the shoes off and feeling the warm tile floor with your feet. But to further know the sun, at no cost, no work had provided that heat FREE!! NIRVANA!
Randen