Any reason to add piste ways directly on top of existing ways like roads? In my experience, it makes it way harder to improve the map when doing non-ski stuff. Why not put piste tags onto existing ways like roads and trails? Doing some research, it looks like overlapping ways is considered an error by multiple QA tools [1] [2] but I'm of course open to discussion on why it might be better for pistes. Let me know what you think!

[1] https://wiki.openstreetmap.org/wiki/Keep_Right/200_overlapping_ways
[2] https://wiki.openstreetmap.org/wiki/JOSM/Validator