The proposal is, for better or worse, quite clear about not providing operator overloading or anything similar in the near future.

You could always offer a method that returns a slice of unique elements, which could then be ranged over.

I don't think there's nearly as much of an appetite for operator overloading as there is for an iterator protocol for range. That isn't to say that the latter wouldn't have a lot to argue over (internal vs. external, etc.) but I think the general usefulness of such a thing would be widely accepted by the community once generics are a settled matter, while I doubt that will ever happen for operator overloading.