I'm 6'0" with a 56"chest and 44"waist. I use sitka gear almost exclusively, with the xxxl jackets and xxl or 44 pants.
My advice:above the waist lightweight sitka base layer for wicking &warm temps, sitka traverse zip for cool weather or heavy base layer (core heavyweight is warm & packs down more, but has very little wind resistance by itself), and the cheapest primaloft jacket (60g or 100g) you can get for layering under the jacket in cold weather. For a jacket, either the sitka 90% or jetstream, I prefer the 90%.
Below the waist: merino boxers, merino bottoms (cheapest you can get in 190-250 weight, check ebay, 6pm.com, stp), sitka core heavyweight, for colder weather a primaloft layer ( ll bean primaloft long John's @ $100, or cabelas instinct hybrid pants - currently $60 in online bargain cave), and sitka pants. I prefer the sitka timberline or 90% pants, size 44.
I also use sitka cloudburst rainwear, pants and jackets both 3xl, the 2xl pants are pretty trim and not as layering friendly on me. The cloudburst rain gear also serves as my shell for rain and really high winds. It is supposedly bit as bomb proof as the stormfront, but is about 60% the price, lighter and packs smaller, and I have put it through the wringer with no damage - it's plenty burly.
I have lived your partner's issues, and found that these work just fine. I just make sure to keep the outer layer optifade - it works crazy good, can't believe the stuff I've gotten way with with deer staring right at me - and the cheapest base layers aND insulating layers I could find under it.
