What if Adaptive Helm's spell damage reduction scaled with bonus mr?

I was thinking how I kind of like (even if it isn't the best place) because it really lets you double down on armor items if you are against a AD heavy team due to its bouns armor scaling. Sure it's niche, but it's really effective in certain circumstance.

Since is already a pretty niche item, what if it was made into a double down item that gives more reduction based on bonus MR. The base reduction would probably have to be nerfed to compensate.