My understanding is that Mozilla doesn't want to support it because you can only get it via Chrome, so if Adobe released it as separate download or offered it as an include for other browsers that could maybe win Mozilla over. I'm sure providing a patch for Gecho and offering to maintain it would help to, after all Mozilla has just started that they don't want to develop it.
Implementing PPAPI in Firefox would be a pretty huge task, which is exactly why Mozilla has no interest in doing so. If Adobe provided the patch, they might take it, but still probably wouldn't. They'd still have to maintain that code over time, and the only use for it would be the Flash plugin on linux, since the other platforms still have flash.