You already can filter items by white / black list.
Is it possible to add skinID to that? Ie, for a blacklist, a player could for instance put the AK item in their bag, but I could blacklist the custom skin that the moderators use.
There are a lot of plugins that reskin items and check the skinid to see if the item is an enhanced version or to, and being able to blacklist these from the backpack would be useful, but making the skinID work both ways (blacklist/whitelist) would enable others to make more finegrained decisions about what could be stored in the backpack.
Another idea, but one I think less practical : can one limit the number of stacks of a specific item? Like a player can put in pistol bullets, but only one stack?