It used to be hard to find ultra lightweight harnesses for backcountry skiing and ski alpinism. Most such gear was made for the rock climbing industry, and designers had trouble looking beyond cliff work to the needs of moderate glacier travel and such. Things got better (for example, with offerings from CAMP such as their Coral, 12 ounces, and Alp 95, 4 ounces).
With the addition of Black Diamond Couloir harness (8.2 ounces) to this category, along with other brands/models such as Arcteryx A300a (10.5 oz) your lightweight harness choices are now a veritable cornucopia of strapology.
I’m liking the Black Diamond Couloir harness. For the call of nature or exit/entry with skis the diaper style leg loops drop completely down with the click of two buckles and opening of your waist carabiner (if you set it up that way, rather than threading the waist belt though the belay loop).
Any harness with buckles on the leg loops can be set up for hygiene needs or skis-on-feet, but the ones with tailored leg loops seem to tangle and confuse me more than the the Couloir’s simple leg loops, which are just a basic strip of webbing that can be easily pulled up and tucked away when necessary.
Couloir harness storage size is amazingly small, keep it in a jacket pocket! 12kN rated belay and haul loops. 8.2 ounces real-world weight checked at WildSnow HQ, could be reduced somewhat by cutting off a few gear loops and such. I’ll probably remove the belay loop as well, since it’ll be replaced by my locking biner. In all, a good choice for moderate alpinism from Europe to Denali