The Houdini packs down in its integral pocket to just slightly larger than a male's clenched fist - thus it always sits in my bag, ready if needed.

I have long carried such an item in various packs. I haven't always needed to use it of course, but when I did, a light hooded jacket to blunt the unanticipated wind and rain was really welcome.

You could also reduce bottle weight by substituting a recycled Gatorade (or equivalent) bottle for the Nalgene. I use both and find the recycled bottles just as tough as useful. You do reduce water volume about 5% (quart vs liter) but knock off about 2 or three ounces in weight. Another possibility would be a Platypus one liter water bottle. It can be rolled up when not in use.

I like the idea of a nested cup. For six bucks, you can get a stainless steel cup that is a perfect fit. For forty dollars, get a Snow peak 700, also a perfect fit and lighter. I'll bet that if you look around, you can recycle a tin can for free...