Thanks SO much, Irulan! Yes, I do agree that lining this jacket would most certainly be overkill. In the photos, you can see the softshell outer layer, and the yummy fleecy lining. You can also see the windproof/waterproof scrim in the center of the "fabric sandwich" too. And besides all that good stuff, this fabric also has a bit of nice stretch to it!

I'm going to make
Jalie pattern #2679, inserting reflective piping in the seams, and also lengthening the back. I'm going to check out some cold-weather jackets at my LBS to see if they put elastic in the back hemline, too.
I'll see if my ANCIENT (1987) serger is up to flatlocking. If it's not, for sure I'll use wooly nylon for finishing the seams on the inside.
The reason why I'm going to all this trouble? Well, I sew every single day in my studio, for one thing. For another, my bust is 36H, and no matter how much I lose everywhere else, the boobs REMAIN (that's fine with me, really!). But this means that there is simply NO women's cold-weather riding jacket to be found for me, at any price...and I'm just sick and tired of wearing men's stuff. I've always wished that Terry's XXL jerseys would fit me, but they only go up to a 42" bust, and mine is 44". I LOVE those jerseys! Ah well...I'll just keep sewing!
Thanks for all your help!