Strangely, they do occasionally do a variant of the Yukon in their sales with a lightweight M1 fabric shell instead of the drishell... but then also use a (presumably larger amount of) less lofty down for the fill so the final weight ends up being pretty much the same for the same effective insulation.
They are quite happy to do modifications to their garments, however... they'll make you a Yukon in an alternative material if you're willing to pay a bit more, but at that point it probably ceases being price competetive with the Nunatak.
Me, I like the safety factor and piece-of-mind that the drishell gives in this case. Its a good bit tougher than pertex quantum, and the down will stay dry much longer in the event of any incidents. I don't ever anticipate being a SUL-er, however ;-)