What If Mordekaiser...
Got reworked, and his ultimate stayed somewhat the same(probably not targetable) but whenever he kills the champion with his Ultimate or while they under the effects of his ultimate, he still gets a ghost of them, the difference is this.
Whenever Mordekaiser casts one of his abilities, the ghost casts their's, or he can control it by pressing R+Q or something to cast Morgana's Snare from her Ghost(as an example).
He obviously wouldn't be able to use their ultimate and their damage would be based on his items not theirs.