It would appear your 'experts' may be experts in installing wood burning stoves, but may have no real experience with using boiler stoves that have been thoughtfully installed. I am a chartered mechanical engineer, and designed my own system to accommodate a wood boiler. It works extremely well as long as you accept the issues that are common with any stove, backboiler or not, and that is the mess they create both in terms of the logs themselves, and the ash clearing etc, and the feeding required. Admittedly these are magnified in a back boiler stove because you are using it so much more, but that's all. Oddly I had a similar experience to this negativity when I went into the local stove store asking about back boilers, mine is getting rather long in the tooth now and will need replaced sometime. The 'expert' was very negative about boiler stoves, saying no-one buys them, so I suspect the issue may be unfamiliarity as much as anything. However one other point that also put me off him, he stated categorically that after 2023 it will be illegal to burn anything other than kiln dried wood!!!! As far as I can see the legislation actually says it will be illegal to sell anything other than kiln dried wood, and that as long as the wood you use is less than 20% moisture content it can be burnt, which can be achieved by correct air drying and storage. If you are burning anything wetter you are daft anyway, as it generates far less heat.
Anyway, to my personal experience and design. I live in central Scotland with my own source of wood. My back boiler was fitted about 25 years ago. It has outputs of 27kW to water and 3kW to the room, a much more effective boiler than is available today. It feeds into a 250L or so thermal store via a 28mm bore thermal siphon (no pump) which goes up to the floor above and across about 2m to the thermal store. If I have the stove absolutely flat out I have on rare occasions heard the stove boiling slightly, but all that happens is bubbles of steam will travel up the pipes, up the thermal store and out the vent, no harm done. The thermal store is also fed by an oil boiler that is controlled from the store temp, so if the wood burner keeps that temp high enough, the oil boiler doesn't cut in. In practice I run it such that the fire does all the work in the evenings, and the oil the rest of the time, this drops my oil consumption to around 40% of what it is without wood use (I have run with and without wood as a comparison) and should allow you an idea of payback time. With this design you have to make sure that the huge quantity of water in the heating circuit (it includes the 250L store) is all properly dosed to avoid corrosion. It will take a few bottles of inhibitor, not just one.
As for wood, yes you need a LOT, but if as you say you have your own supply, like I do, then that isn't an issue other than having to generate it, which is in itself good exercise. One trick that not many people are aware of for creating firewood that doesn't require the wood to be stored for a year is as follows. Fell your tree in summer, preferably in one piece, leave the felled tree on the ground for 3-4 weeks until the leaves are all crispy, then chop/split it into your firewood lengths, if you test it at this point with a moisture meter you will probably find it is already below 20% and ready for the fire. If you chop branches off first, or before the leaves are crispy, the main trunk will not dry so thoroughly and will need additional air drying.
I have more recently also added in a solar element into my system, I have 14 panels (nominally 3kW, bought cheap) directly connected into an immersion element in the thermal store (actually 2 of 3 x 1kW 3 phase elements which on sunny days runs inefficiently as it max's out at 2kW with just 2 elements connected). From early April until late Oct when the heating is off, I don't need any external energy input to get my hot water needs met, and I use it in my dishwasher (fed with hot water instead of cold) and my washing machine also (I have a dual feed washing machine). Anyone who says this is pointless because of the lag in getting the hot water to your machines is wrong, all you do is run the hot in the adjacent basin until it runs hot before you run your machine. Direct coupling solar panels however has to be done carefully as you are talking high DC voltages, and appropriate isolating switching, earthing etc is required, your standard 240Vac switches won't cut it. I have designed a control system to control the output using an Arduino and solid state relays so that I can connect all 3 elements and run the system in a pseudo MPPT form by balancing the applied load to the panels output, but as yet I haven't built this system, albeit I have tested it in a simulator so am confident it should work and when created will increase the solar input.
I have like yourself an interest in IoT and my thermal store is kitted out with a wifi enabled thermostat that drives the oil boiler and allows me to monitor the thermal store temp and judge when more wood is needed to be put on the fire. The oil boiler 'set temp' varies during the day so that in the evening when I am running the stove, it is at the minimum temp needed to run the central heating effectively (35C), rather than the temp required for hot water (45C) which is the set point in the mornings. This ensures the oil boiler cuts in as little as possible when the stove is in use.
