Welcome Jeffg10!
Rusted Items
There are some items that behave like this.
You'll find rooms filled with debris and damaged items in certain areas, and there are other types of items that degrade as you use them (though not many).
It could be expanded a bit, and I
do rather like that idea about adding variety to the early game like this! More powerful stuff from later on that clearly won't last as long, but in the early game it could be fun to use for a bit.
Actually, it kinda falls in line with what I'm already doing--technically there are ways to get a few mid-game items out of depth early on, something I plan to continue adding more of. (You need to visit "the right places"
)
Specifically with rusted higher-level parts, I can see a small lore issue since it doesn't make a lot of sense to have old but powerful items that far down in the complex... but I'll keep it in mind. There are definitely more item concepts in the works already, just very low priority right now compared to other features.
Uniques
I can't comment on this because spoilers.