I have been following your thread on this moped/snoped thing,
I think the way to deal with the clean, dry road crossings would be to leave your front tire on, design your front ski like those on some airplanes. The front ski will mount via struts to the front forks and have a slot that allowes the front tire to extend an inch or so below the running surface of the ski! The tire will loose contact with the ground when the snow is deeper than an inch and act like a rib to help the tracking.
BTW if ya want a copy of a snorunner manual, let me know, I'll make ya a copy.