Verification Rule Question Regarding Items

[AntaresCD]

Forgive me if there is an obvious or standard solution to this that I've missed, but here is my situation and question:

I have one category of items for my units that all units have a default limit of 1 of (enforced by exclusion groups and appropriate tags). There is another item that can be taken by some units that raises this limit to 2 but carries the restriction that if they take 2 items from that category they must be different items. The first part is easy (raising the limit) as the exclusion group is tied to a hidden stat and I can just add 1 to the stat. The second part is what I'm having trouble with.

I've explored different ways of trying to enforce different items being taken but they seem too unwieldy or very brute force (and therefore hard to maintain as the list of items in that category grows).

Any ideas or suggestions would be appreciated.

Thanks,

~Antares