The amount of work it would take to fork Chromium and maintain a working secure browser with MV2 hooks into the browser internals would be so large that you'd need a dedicated team whose job it is to constantly backport upstream Chromium changes and ensure they still work with the old MV2 subsystem. That would take a lot of time and money.
Well you don't need to implement every stupid thing big G thinks should be in it, just the really critical stuff. Even if you freeze all features right now you'll probably still have a better renderer than gecko for 5 years into the future.
I mean right now I bet a lot of people will simply not update to MV3 and continue using the last known MV2 build into perpetuity until certs break or something else. I sure intend to.
Backporting from an entity that is hostile towards MV2 makes me suspect that Google isn't going to play ball and make maintaining an MV2-compatible Chromium fork easy.
