Quick J58-WS update. Just arrived today. Fits exactly like I was hoping (I'm medium, 32 waist, 40 chest, 182cm 80kg). I can layer thinner things under it and it was fine (thinner fleece, but not a chunky sweater for example). Walking around I didn't find it bunched as someone mentioned. The warmth is great, and the pockets are huge. I don't have the previous version as a reference though, so comparisons are limited.
My only hesitation is that the material feels quite delicate, including those in the pockets. I feel like that might give me pause at times (my philosophy is to wear things fairly hard, especially if they're expensive), but unsure what experience and perspective others might have with this material.
Anyway, overall I've never owned an insulator that I've really enjoyed wearing independently, and have struggled a bit to find one that blends in with other pieces when layered. This definitely feels like it will fill that gap, but let's see.