I'll answer anecdotally.
I started lowering the weight of my pack by
- weighting stuff I put in,
- considering whether I need each item or if it could be replaced,
- considering that some cottage or myog could be as or more efficient for less weight
The first home-made gear I used was a sleeping quilt. It is good to ~0C comfortably, is synthetic (2 layers of primaloft 133g/m^2 - that's 4oz/sqyd) (because around those temperature you get a lot of cold humidity), weights ~850g, and fits in a 13L bag without effort.
Now, for UL, that's still heavy and big. But that's still much better than what I had before, a 1.3kg 5C bulky bag. Also, it is a quilt, which I find way more comfortable (for those temperatures. Below, I would still use a sleeping bag).
Several cottages have quilts that, beside being lighter, would be more comfortable that traditional sleeping bag.
As for shelters, I find that I prefer tents that use straight poles vs domes (e.g. the MSR twin sisters). I find them easier and quicker to set up, simpler and more reliable. (and also lighter, but that's just a bonus)
There are cottages that offer that kind of shelters using various fabrics, in various sizes.
Clothing is more tricky, because you want to test them before wearing them. (And making jackets yourself is extremely long, I find.)
Packs, finally, come last. I find it a much more complex piece of equipment, and I find anyway that comfort comes first (once the volume is decided, based on the rest of the stuff). Comfort is obviously hard to test without trying the gear. I would probably not consider a cottage pack, unless I could try it from someone.
Overall, I would recommend considering cottage gear not solely in a weight reduction perspective, but also because they offer different shape and type of gear.