I would love to see a system where we had a Unique upgrade process, borrowing some concepts from the Poe2 reforging bench:
3 LP0 uniques (same unique item ofc) could be reforged to one LP1 unique where the modifier values are rerolled.
Similarly 3 LP1 uniques reforge to one LP2 and so on until LP4.
This would be especially beneficial in CoF where every unique item contributes to your progression instead of being useless unless it has high LP/good rolls. Almost every unique drop would turn into a potential upgrade at a later point in time
This is a frequently suggested system. The big issue is with the relative rarity of each stage of LP being different. So each unique would have it's own number to combine and it would have to be way more than 3:1.