The general case would be to have text written in the same paragraph align well. To me that encompasses same baseline, same x height, and in the case of mixing

The general case would be to have text written in the same paragraph align well. To me that encompasses same baseline, same x height, and in the case of mixing scripts same cap height (in case of CJK). Basically “do what I mean”. I understand that it’s hard, but it should be at least doable. If it would require being able to specify which height to consider, so be it, make it an option.