I just got off the phone w/ Ben (goosefeet) and he's never had anyone ask this question or knows of anyone that has tried it, but thought that for infrequent use (not a 30 day expedition across Alaska) it might work- might being the key word as he obviously can't warranty any damage resulting from such use
My intent is that these are going along anyways for use at camp, and the trips I would anticipate using them as part of shoe system would generally be milder temperature wise- so a Below40 or NEOs type over boot would be overkill and unnecessary IMO-this would be a stop gap measure to use them say in the morning for a few hours until it starts warming up
I guess the other option would be to fashion up a DIY Tyvek over-bootie?