Note, my jacket is an original PeakXV from the first season it was release...the lining could have changed since then. My jacket only has a small napolean style stretch pocket that will not fit anything more than a wallet or a couple bars, etc.
I had thought about adding a pocket, but it's not an easy task. The lining is extremely light (feels like a 15d fabric) and considering the weight of a full nalgene bottle...you'd risk tearing open a large panel in the jacket if that bottle bounced. Also, the jacket is fully baffled, so I wouldn't trust a local laundry to start dissecting the jacket...not a lot of tailors deal with down, and even less with fully baffled garments. I've looked it over many times, and it would be pretty complex and involve reinforcing the 15d lining by placing heavier material behind (either through the hand warmer pocket, or by removing the lining, adding a reinforcing fabric panel, and then re attaching. There are a few other options, but none that I could pursue with absolute faith in that the jacket will retain structural integrity.
Sorry OP, I have no means of verifying the original down fill content...I believe I saw a post on BPL stating that someone called customer service, and those were the published numbers.
Maybe Richard can post a new clo rating for the newest version of the jacket?