I like that this thread has a number of differing opinions. Reading it has one swaying back and forth with the perspective of the poster's experiences. It is also an older thread, so I am not sure it if the Wallas diesel stove/heater option was available for overland campers when the OP was pondering this, and other options are now available.
The Wallas $2,800 price tag is more than double of what you would spend for a nice SMEV two burner propane cooktop (are they about $400?), and then adding a propane furnace, such as a Propex at about $800 or a D4 at bit higher price. Despite the cost, the Wallas seems quite popular now, most likely because it makes a good heater?
For my .02 I would still stick to propane for water heating and cooking, and go with the D4 for heating, substantially reducing propane use/requirements and hence tankage and/or refilling. From my experience, the biggest PIA with propane has been both the typical RV furnaces (which suck a ton of battery and are noisy) and the refrigerators, which run a pilot (which I would imagine creates the largest propensity for accidents for those who see propane as unsafe) and the venting requirements, which add yet another hole in the roof, that most of us try to avoid. I have also had some fairly expensive adventures with RV Fridge boards, etc. that I would sooner forget. That leaves an efficient 12V fridge as the best option, particularly with the advances in battery technology, controllers, etc. with solar.
Suburban DSI Water heaters are easy to drain, and it is nice to simply hit the switch inside the rig to turn them on. I like the fact that you can also heat water with 120VAC if you get that option. I have never frozen one, but have dry camped it below zero, so IDK how low you can go with one of those. I had a 1978 GMC MH that heated water from the engine, so it is not a new concept. Nice to always have hot water on the road, without burning propane. I agree with the opinions that it would be difficult to have a removable unit that shared engine heat, but on the GMC, it was a simple set up that was very effective.