A better tank item that bruisers and mages can't abuse!

So everyone knows that tank items are kinda garbage right now so I was thinking of at least one possible way to buff them without letting a lot of bruisers and even mages abuse them. So my idea would be a new passive that would provide extra health or resistances if you're under a certain threshold of attack damage or ability power, this way carries wouldn't be able to get the full effects of the items while tanks would.

Say this passive is on an item with 400 HP and 60 Armor, If you have under 250 AD or AP you gain an extra 250 health or something like an extra 20-30 armor or MR. This would largely prevent champions like Irelia from using the item to it's fullest, but a tank like maokai or sion could use it much better.

I'd be willing to bet i'm not the first person to think of something like this, and I can already foresee problems with things like baron buff or even yummi giving stats, But this was just a thought I had that could potentially give tanks some tankiness back without making carries even better. Please tear it apart and tell me what's wrong with it, i'm genuinely curious to hear the things I didn't think of!