Cassie. I know I'm biased but hear me out.
She was perfect in MKX. She had a unique look, had her dad's sense of humor but her mother's heart and work ethic. This is how you do generations. She can stand out on her own, but was still clearly Johnny and Sonya's kid, and it felt like she was raised by them. I know people don't like guns and blah blah, but at the core of it, Cassie was a great character regardless of which faction she was part of. I think they missed the mark with her in 11 in too many ways (voice actor, no undercut, more preppy than she should be etc.,).
BUT, If Cassie does make it in MK1 as DLC, whether that's as a Kameo or a full character, I think they'll defo be able to bring that original MKX vision they had for her.