Mordekaiser small rework idea

Currently, I think Mordekaiser is in a weird spot. Riot reworked him awhile ago to be a "juggernaut that can go bot lane" essentially despite itemization keeping him mostly as an awkward split push mage fighter thing. I think part of the issue is with his passive. I've come up with an idea on a rework to it that may make it a bit closer to that juggernaut vision without totally changing him. Its basically a total rework of his passive. Currently he fills a bar under his health when damaging targets with hjs abilities. This bar acts like a shield that decays at a stupid fast rate. Its also not clear what it gives in terms of a shield. Since its a full bar and not an actual shield (nor is it treated as a shield) you can't get a good indication of just how much it will block unless you click on Morde to see the passive's current max value. Even then Yas has a similar effect for his passive and that turns into a shield when it triggers, so here's how I think you change it:

Passive: Master of Metal Killing/assisting a unit or damaging them with an ability rips part of metal on/in their body and siphons it to Mordekaiser, granting him a stack of Metal Body. For each stack he gains a bonus health equal to .5% of his base health. Additionally, whenever he gains a stack he gets a sheild equal to a small % of his current health + 15 health per stack. Shield cannot stack with itself and can only trigger once every 20 seconds. Gaining stacks while shield is up adds that bonus health gained to the current shield and resets its duration. Ability health costs are boostsd by a small amount per stack.

Change to E to accompany this: E expunges current shield, dealing bonus damage based on shield's strength. If it hits an enemy champion a portion of the shield is refunded for each one hit.

Its more late game focused while still making him awkward to duel against. Thoughts?