In reply to Iwan:
I haven't been ski camping but have used a pulk plenty of times and I used a TNF Himalayan Parka down to minus 38 ish? and I was toasty bordering on the too hot on some occasions.
Not exactly lightweight but it was strapped to the pulk when I wasn't using it. I think is was about 1.5 kilos and a godsend when it was baltic.
It does pack down surprisingly small, depends if you want the extra weight.
Failing that, a PHD Xero jacket is probably the way forward.
Hope this helps, Den