i mean most of the "base" of Mordekaiser is still there, unless you mean theme-wise in which case the spooky magic would just be another SI champion and mord would be a metal man again
It's the execution of the rework that irks me the most. Q feels incredibly unsatisfying (both visually and gameplay-wise); E is somehow less satisfying (needs to be changed up; rework it as an ability with more counterplay and more reward). W just needs to have more "oomph" factor because it just looks awful and feels bad to use.
I'm iffy about his ultimate. It's a very defining aspect of his kit and it is one of the most unique and powerful ultimates, but the more I think about it, the more I worry that it's holding him back. It eats up a large portion of his kit and is the main reason he becomes so difficult to balance at times. Would he be both better off and still iconic with a new ultimate that further emphasized a power over metal? Sometimes I wish League could handle more than 4 buttons for abilities.