A better solution would be to just get Firefox to support NativeClient. Especially as Unity 3D (an another two major game engines I can't disclose atm) are going to support NaCl as a target in the next year or so. Funnily enough, they're using that to claim Linux support without any "native" Linux binaries.
That's sort of like suggesting they use Flash instead of WebGL. Probably a great idea in the short term, but rather missing the point of the exercise.