"[butanol] would be a really bad choice for almost all alcohol burners used by hikers. It would be even more smokey than Isopropanol..."
Have you actually tried burning butanol? From what I've read, there are additional reasons why isopropanol happens to be abnormally smokey and butanol can actually burn cleaner than ethanol while being less corrosive and 20% more energy dense (36 MG/gram vs 30.5 MJ/g). Obviously you'd need more oxygen, but butanol also seems to have a built in inhibition against forming carbon monoxide and other noxious fumes. This isn't really backpacking stoves, but a car running on pure butanol will have far lower carbon monoxide and noxious emissions versus a car running on pure ethanol.
I've spoken with the Chief Technical Officer for Green Biologics ltd (company R&D'ing bio-butanol) and he said that if you put butanol in a dish and light it, it burns really cleanly just like that. I might be able to get a hold of some butanol at the chemistry lab at my university.