Might be worth trying a hammock in mild conditions to see how you like it, then looking in to underquilts and stuff. Hammocks just get heavy and/or expensive to do cold weather comfortably. I do sleep better in a hammock than anything else.
Cold weather hammock camping can get expensive, but I don't think it's any more weight penalty than other options, unless you are using a bivy type system.
Here's my hammock setup and I'm by no means on the light side-
PolyD 11.5' Hammock- 10.8 Oz.
Hammock Gear Incubator 20* Under Quilt- 25.1 Oz
20* Down Top Quilt I made from a sleeping bag- 28.7 Oz
Warbonnet Superfly Tarp- 22.7 Oz
Suspension, 6 stakes, other- 10.7 Oz
Total Sleep System- 6.125 lbs.
I've taken that setup comfortably down to 15* on multiple occassions. I also have a zero degree underquilt that would add about 5 Oz. Throw in a second top quilt rated to 45* for another 16 Oz. and I'm good to zero degree weather.
If it's warmer, I can use my 30* hammock gear Burrow Econ and drop about 7 oz. off the top quilt. Change out the tarp for one without doors and I lose another 5 oz. I could probably ditch a few stakes and other miscellaneous hardware for another few ounces as well but I choose not to.
Again, my system is set up for comfort, not weight savings. Since I spent the time to learn how to properly use a hammock I've been sleeping much better in the backcountry. They are not for everyone, but they can be very comfortable. My point is, they aren't going to be much different weight wise to a standard tent type setup. The money I've spent on multiple under quilts, top quilts and tarps has been a disadvantage but a good nights sleep is worth it to me and my system is very flexible for about any weather conditions I'm likely to encounter.