Here's the CWC jacket:


And here is Simplicity 4045, the jacket I'm using as a jumping off point:


I'm sure there's a pattern out there somewhere that would need less changes, but I like a challenge and it's been a while since I did something like this. Plus, I already had the Simplicity and there's no way I was going to wait on an online order or venture out into retail-land on Black Friday.
After studying both jackets, I decided I needed to change the Simplicity pattern as follows:
1. Create separate neckband pieces.
2. Add button plackets. The Simplicity jacket meets at Center Front and there is no allowance for buttons and/or placket.
3. Create front princess seams from the bust darts, and, of course, do an FBA. The CWC jacket has armhole princess seams front and back. The Simplicity jacket has a side panel. I decided that was close enough so I'm leaving those seams as-is.
4. Add a Center Back seam.
Below is my pattern morph. The original Simplicity front/side combo piece is on the right. I cut out the tissue, did my FBA, and then traced the results onto a new sheet of tracing paper. The Simplicity pattern is taped back together. I figured if I was way off base, I would want as much as the original as possible to go back to. I then closed the side bust dart on my tracing and created the princess seams.

I decided on a shoulder princess seam for the front instead of an armhole princess seam. I'm going for "essence" of the CWC jacket, not an outright clone. Shoulder princess seams are more flattering on me.
After making those initial changes, I made a quick muslin from an old sheet. The neckband and plackets had not yet been completed for the muslin. I was merely testing fit and landmark placements. So far so good, although I decided I needed to (1) add another inch to the overall length, (2) move the shoulder seam backward 5/8" as this seems to be drafted for forward shoulders, which I don't have, and (3) shorten the sleeve about 3".

Here's a shot of the panel seam. You can see there's no actual sideseam. The panel is seamed toward the back.

With the fit tested, it was time to do the final fit tweaks and create the "missing" elements. I drew the neckband pieces and cut them from jacket body. I made the placket pieces and added seam allowances where they'd be attached. I lengthened/shortened in the places I noted. And thought I was done, until just now when I realized I forgot to cut apart the back piece for the back neckband. Oops. I'll have to do that tomorrow. My pattern brain is fried tonight.
I don't think I'm going to do another muslin, but I will pin all the pattern pieces onto Zillie to be sure my thought process worked for the construction and that I'm not missing anything. I haven't done a ton of jacket linings so I'll curl up in bed tonight with some refresher info to make sure I don't forget anything with that either.
Hopefully before the weekend is over, I'll have a new jacket. Now that I have the new A/C, the temps are supposed to be in the 40s (F) tonight. Figures.