How is it half of HN is convinced Firefox can compete with Chrome in its entirety and the other half is convinced nobody can possibly maintain a single additional API version on Chromium?
As a counter example, Brave is heavily invested in C++ and Rust, and I believe they could handle that work much better.
Even if they don't want to handle it directly, this is the kind of thing a single sponsor can pay Igalia for, who have shown the ability to make entire new Chromium subsystems like MathML. There is no shortage of C++ browser developers in the world to do maintenance work.