Mordekaiser is unbalanceable.
Forget that his rework made him into more of a bot lane champion. Look at his kit. What's his identity?
He's split between a shield stacking mage and a bursty melee brawler. None of those identities are healthy.
Could you imagine if Rumble's flame throwers also gave him a perma shield? Could you imagine if Jax's passive did 9 times its normal damage at the cost of his gap closer and stun?
The most interesting part of his kit is the ghost mechanics. Dragon ghost is strategically a cool addition, and the idea of turning a five v five into a six v four is also cool.
But I can't imagine Mordekaiser's basic abilities being retuned to anything other than over powered or garbage.
He has no gap closer, his MS boost is negligible, In case you didn't notice, he can't really duel late game either.
When he's in a massive team fight, he magically picks up pentas, when he solo's a Zed, he gets smashed.
He's the most kiteable of the Juggernauts but in order to not make him into a melee urgot he's gotta do a lot of hurt.
And G&B will never give him a gap closer for fear of him just turning into a watered down Jax. (actually giving him a Fear rebuff would be kind of cool)
But the main thing is his numbers can't be reduced without hurting him significantly.