This is how the Godfather of steep skiing used to train in the off season, what do you think?
"to me, the people who can ski on the stones can ski in any type of snow"
Well, he's not engaging the edges before the fall line, so he must not have much skill. J/k.
In the U.S., a lot of the places that might be good for this in some ways are places where impact, regulations, and safety might prevent it, imo.
Scree skiing in sneakers/hiking boots and Nordic running on very steep slopes are both great crosstraining though imo.