Morphic the Shadow Morph

I had this idea of a champion that could morph to another champion to learn its ultimate or any other ability. Say for example, you are in a team fight and there is an amumu on the other team. Morph into amumu for a limited time and learn their abilities. OR use R-Q to learn one ability of that champion, in this case amumu and have the morph go longer because of only being able to use amumus Q. Feel free to post opinions i just had this idea for a couple days.definitely could use brainstorming.