Riot would have to aesthetically ruin Amumu for him to be accepted as a Mummy Boy.

Everything about him is out of proportion for a human being. He's quite clearly a Yordle-type character and to me that was always implied. Why, now, is he some random dead kid? Not to mention I hate having humanoid odd-ball champions. He's completely out of place in Shurima. Even if he was a Yordle Mummy he'd be completely out of place in Shurima because, unlike Gnar, he has no physical features that indicate that he had adapted to possibly survive in the middle of the Shuriman Desert.

His new lore is nonsensical, tacky and simply leaves me unfulfilled.

I'd sooner accept him as a Gothic, Dark Fantasy-type character from Zaun or Piltover than a displaced Mummy Boy lost in the desert.