It's gonna be Amadeus Cho. The "Totally Awesome" title and supposedly more jovial attitude fit (as does editorial's line about it "pissing off" the same people who got mad about people like Miles Morales, Kamala Khan, or Jane Foster) and I'm guessing the mystery character is Cho's sister. Pak's Hercules run had a subplot about Amadeus finding out his supposedly murdered sister was still alive, but I don't think it was ever resolved, nor was she seen in person, before the book got cancelled.