That sounds really, really hard. It might be possible to learn it though, if you started out sitting on the seat, or at least seat in front, to get used to the awkward motion. Once you were adept at doing it seat out, you could learn it with the seat dragging. Doing it backward should also be possible with practice, and might even be easier.
And yeah, I guess keep switching… except now that I think about it, maybe it would be possible to do it without the switch, it would be hard because you’d have to somehow take the weight off your “crank foot” until the pedal comes round to the front again.
Momentarily have both feet on the wheel?
Not an easy trick my any stretch of the imagination.
It may be possible to do it as an idle first before learning it as a riding trick. I can imagine it being done as a kind of seat drag/one foot wheel walk/crank idle hybrid, though I can’t imagine it being easy. Maybe learning seat drag crank idle would be helpful…