To answer your question about the lining, I used a fuzzy-backed lining fabric specifically for coats, which is warmer than plain Bemberg rayon. I also interlined it with a high quality cotton flannel. I’m not sure that Bemberg alone will help block the wind, unless your wool is very thick and very tightly woven. You coat pattern is rather dressier looking than the one I made (which was a raglan style), and too many interlinings may bulk it up too much, so I’d skip the interlining. On the other hand, since you’ve already bought the lining, maybe a flannel interlining would be good to add, since it is layers that create warmth. Also, since you’re ditching the skirt (which on the one hand is a nice detail, but on the other, maybe a little frou-frou, too, I think) make sure when you make the muslin that you have walking ease.

So, to recap, check that the muslin will fit over any bulky sweaters or suits you might wear in the winter (unless you know you’ll only wear it over dresses), and that you can do a decent stride without the lower part opening up on you with each step and letting in the wind.