It would take a special buyer to appreciate the work, value and future savings of a wood boiler. Same goes for a high end wood stove. Most people just wont get it. And they wont want to feed it. People are lazy and set in their ways. When people hear wood fired water boiler around here their mind immediately goes to things like Wood Doctors, and the smoke they make.. Mention gasification and their eyes glaze over, "Gasoline", they say, Why would I heat with gasoline, its too expensive!!"
If (when) I build my new place the wood boiler will be in a separate building I think. And it will be designed with future removal (either for replacement or sale of the home) in mind. Id likely offer it with the home, like say $10000, and if they wont buy, then out it comes. I'd probably build with electric baseboard as backup anyways, so if the purchasers didnt want the boiler, they'd be left with an electric heated home.
Where I think things change is "Solar". Either solar water heating or PV electric generation. Most people are familiar with solar so that would help the value. Plus most of us are tired of the local hydro raising rates and would like to stick it to them in some way
On top of that, and most importantly, solar doesnt require near the effort of a wood boiler.
People will also understand the value of and pay for Geothermal heat pumps.Established "push button" technology that people have heard of.
Now, if we were in Europe and had bulk pellet delivery like they do, just like oil delivery where it's no muss - no fuss, then I could see a boiler being a selling point. It comes back to most people being lazy and want nothing to do with the labour involved. They want "push button". Money savings are just a bonus.
Same goes for nicely piled rows of dry CSS wood. 99% of the buyers would see no value in that. Remember, most people just use the stove for ambiance and will burn wood that was fresh cut last weekend
Of course there are exceptions to these rules and that would be the 1 in 100 buyer you'd need to find to get your investment out.