I'd think that though a multi-fuel CAN run on straight, raw WMO, you'd rather at least run it through a filter first to remove all the solids it picked up from the last engine it ran through.
As far as uses for WMO, there's one application I'm wondering about...
Wood Doctor - Outdoor Wood Furnaces - Installations
The combustion chamber is essentially just a cabinet lined with refactory brick. The steam heat pick up pipes are in the top. There's a means of introducing air at a controlled rate, an exhaust shaft, and a door for adding logs.
Now, to extend the supply of firewood, and to utilize an otherwise waste product, what would it take to plumb in a sort of sprinkler system from Hell? One, two, four, etc discharge heads at the end of a bifurcating tubing structure capable of withstanding the highest temps the furnace could produce. Have a pressurized WMO feed controlled by a solenoid valve, essentially EFI, if it were designed by a mental defective. Slaved to the same system that throttles air intake, it would just give a short burst of WMO through already heated pipes right into the center of the combustion chamber at calculated intervals.
I wouldn't think a constant feed would be a good idea. I'd imagine unburned oil seeping through seams in the refactory brick and pooling in the bottom where it would conduct heat to places the heat ought not go and damage the furnace. Just flashes to coat the white hot coals and insure a complete combustion.
Since it's just a basic wood furnace, there's no fancy-schmancy octane sensors or MAF... well, there may be a MAF. I dunno, but at long as the furnace has enough air to combust whatever it has for fuel, subject to its occupant-set thermostat, it's happy. Whatever energy is liberated from the WMO extends the time until I'd have to trek out with the wheelbarrow and bring in another load of cord wood. I'd also plan to burn all manner of paper trash in this thing.
As long as the combustion chamber is kept hot enough prior and subsequent to the introduction of the waste paper, it should be a fine, clean burn. Minimal soot, and a near straight shot, five stories up and out the chimney. Has anybody heard of a product called a "Super Chimney"? Supposed to be a square metal duct on the outside, round metal duct on the inside, and in between a dense fiberglas matrix. Only needs 2" to combustibles.
As to having multiple fuel tanks that are switchable, I'd think the DOT cops would have seen it all by now and would be wise to that. I read a story about one crooked trucker who had rigged his truck with an "active" suspension so that it would "lift" the axles as he rolled over the scales, so he routinely weighed in as half what he actually was. He also had a stolen EZ-Pass. Just took one DOT cop to pull him over and that subterfuge got his but thrown in jail. I wouldn't think a trick fuel tank would be a challenge to detect.