Now I'm no alpinist, just a regular girl, but I've been lightening and lightening for the last few years, and I've learned a couple of things:
Taking a lighter sleeping bag rated *right* at the temps you might encounter will lead you to freeze your butt off. I had a few shivery cold nights this year by trying to save a little weight on my choice of bag. Maybe it's because we women don't stay as warm as men, I don't know, but I'm starting to rethink that part of the system. Last night I slept under the stars in a 10 degree bag and the weight savings versus a tent was a good thing. It was a synthetic bag and only for one night so it was a good way to try that out. Wasn't half as bad as I expected, and it was a little chilly last night.
Hats and gloves are way lighter than coats. I think a Primaloft vest might also be a good addition.
Food always weighs too much. I wish food could both taste good and be light.
A water filter weighs the same as a half liter of water. Even if you never get sick from Giardia, if you carry it, you spread it. Same with dogs, though if you bring them in the backcountry they are going to get into the water no matter what.
Softshell stuff makes a reasonable sub for rain gear if you don't expect a lot. They make a lot of stuff out of softshell fabrics these days other than coats.