I have searched and don't believe anything like this exists, but I was thinking about a crampon (no spikes) like apparatus that you would strap to the stiff boot of your choice and in the front of that system there would be a hook up for an BC NNN binding. So one could take mountaineering boots (plastic or leather) and step into skis like my Rossi BC 70s. My Alpina BC boots are okay on skiing with, but if I have to hike or anything like that, they are not comfortable.
Anyone ever seen a strap on system like that? (not sure if my description made sense)
but they suggest a boot with a flexible sole.