lilleyen said:
Maybe gators or chaps then?
I see a lot of "bikers" and riders who wear leather chaps whenever the temperature gets even moderately chilly, to combat the wind-chill factor. I think that would be a great way to make the rear passenger more comfortable even on a fully-faired scooter.
I see a lot of "Goldwing Couples" out this time of year wearing matching "snowmobile suits." That's a possibility you might want to look at as well.
The few times I've been caught out in cool & damp conditions, my legs got cold despite the fairing. I pulled over and put on my rain pants (and rain jacket once on the Oregon coast when it got
really cool and damp), and I felt much more comfortable. Since I always carry my rain suit anyway this isn't something I have to remember to bring. Although rain suits aren't designed for insulation, they are pretty wind-resistant and provide an extra air-trapping layer over whatever you're wearing under them. Considering the relatively low cost of a good motorcycle rain suit (my is a Nelson-Rigg brand), I recommend that as the first step.
HTH.