Shannon offered one more suggestion to eliminate the diagonal lines; a tuck between bustline and waist. I thought, 'Well, that's a simple thing,' and sat down and did it last night, before I started disassembling the jacket to mark the pattern changes.
When I first looked in the mirror, my reaction was 'Wow! they're gone!' I made DH take a photo.
When I looked at the photo, my reaction was 'No, they're still there.' And it's beginning to look a little over fitted. So I took the tuck out; we'll see what, if any, difference interfacing and lining make.
Meantime, I've been reading up on fold lines in sleeves and think I need to reshape my sleevecap slightly for the forward shoulder thing...hopefully that will eliminate a lot of that drapey stuff that's going on in the sleeve.
Disclaimer, just in case someone's thinking I'm going to too much trouble: This is not my normal fitting routine; I'm being extra picky here because I intend to use this jacket as a basic pattern. I've made...and worn...and been happy with...other jackets from other pattern companies that fit no better (or even worse) than this one did originally. Part of the reason is that I really, really want a well-fitted jacket; part of the reason is that I just felt ready to tackle and learn some more about fitting and I can't afford to spend a week with an instructor. So all you 'Internet Friends of the Lisa of the Laree' (:D) have been taking the Instructor's place.
For which I thank you from the bottom of my Janome. (Gee, if I used a Bernina it would've been so much more poetic...)