alt Hacker NewsStaff SWE at a FAANG here.
Fabrice Bellard is not a 10x engineer, he is a 100x engineer. You could attach him to a good people manager and either build a team around him or allow him to work independently on a project that he finds exciting that also aligns with company goals.
I think you are mixing up art, technical skills and productivity.
Put Terry Davis (again him) as senior manager at Apple, and see the result.
From my point of view, Terry has the same level and approaches as Fabrice.
It does not guarantee at all that he is going to be more productive than 100 engineers as you directly claim.
It makes them good in what they like to do (writing obfuscated or low-level code, or implementing from scratch from specifications) as art or creativity.