Changed construction order for fitting Simplicity 1540

 This is for View A. My guess is it'll probably work for the other views, except maybe C, but I haven't verified that.

1. Finish that little horizontal seam across CB completely, including the tab and the topstitching. (This assumes you don't need to do any fitting on that seam. If you do, you'll most likely have to adjust the side backs to match somehow, which may involve at least partial recutting of those pieces.)
2. Get a rough idea of the fit by sewing all the torso pieces together (either baste or not, though boiled wool is slightly annoying to unpick; your call). The goal here is to get the torso to the point where you won't have to make changes to the shoulder seam inward of the princess seams, or to the neckline/CF edges. You can work on the princess seam/side seam fit a bit at this point, but don't do any topstitching of the princess seams.
3. Stitch the inner parts of the shoulder seams permanently, just far enough to give yourself something to attach the collar to. In any case you should stop short of the princess seams. Press those areas open.
4. Make the collar. Attach the collar and the facing. (I'm doing this in a different way than given in the instructions as well, so that I can have two pressed-open seams instead of all four seam allowances being pressed into the facing. More on that later.) The facing doesn't need to be stitched all the way down CF; you can stop short and leave the hem part for later. Press those seams and understitch as you normally would (again, stop short of the hem if you want to leave that part up in the air for now; you can always do the rest later).
5. Check the buttonhole placement; mark and make the buttonholes and sew on the buttons.
6. Make the top parts of the sleeves and set them in temporarily. (Or you can do this after step 7.)
7. Now you can try on the coat with a real closure and a firm, faced/interfaced front. Fiddle with the side seams, princess seams, and princess darts as needed, as well as the tips of the shoulders. Go back and forth between fitting it with and without sleeves, as needed.
8. Once the torso/shoulder fit is established, you can sew those seams permanently, topstitch the princess seams, and put on the pockets (check whether they're placed at the right level first).
9. Make sure the sleeves fit well before setting them in permanently. You can test them with and without the bands. The sleeve/band seam would be a place to change the length if needed. It'll be easier to topstitch with the sleeves off, but doable either way.
10. Finish the hem.