An alternative to consider: What if there was a way that didn’t require them to be unique?
I really like instanced objects and the power they can allow for extensibility from multiple sources. In my experiences so far, I’ve usually found it best to tackle this problem (at least when dealing with arrays of them) to assume duplicates and factor that into the design.
Think of it similar to components. Imagine if you were limited to a single mesh component, awfully limiting. Or take an component that manages inventory. It could make sense for that to be unique to an actor, but you open up some design space if you’re not so rigid. Perhaps one inventory is what is equipped, one inventory is your backpack and one is the bag-of-holding you have equipped. Just an example.
I’m not suggesting that you’re wrong to attack it with an eye to uniqueness, but reframing the problem to not require uniqueness has come up a few times at work when reviewing designs by junior engineers and it’s always worked out for the better for us to drop that restriction one way or another. Worse case there are some duplicates that are redundant but don’t cause a problem to coexist with another instance.