That's unsustainable. It's what some projects already try to do with Chromium, and it just doesn't work: every time Google steers a bit more towards evil, the downstream burden increases significantly, and sooner or later the bad patches creep in anyway.
There is an institutional problem at Mozilla, we should focus on fixing that rather than trying to come up with even more complex sticking plasters.
Whats needed is a rebirth, basically the Mozilla team quits, creates a new mozilla inc and leaves the old one behind to go full chrome appocalypso.
Basically what nature does when the elder generation acquires to many parasites and dna damages, spawn a new generation and die, taking most of the parasites with them.
> There is an institutional problem at Mozilla, we should focus on fixing that rather than trying to come up with even more complex sticking plasters.
How do you fix that from the outside if not by forking or at least using a different Browser to make it clear that the current behavior is unacceptable.
Forking is an option only insofar as the forking team is actually capable of leading development. Purely reactive forks, like most of the ones we see in the Chromium world, are not sustainable in the long run. Is there a team, out there, who could fork FF and take it into a new direction? Maybe. But that has happened only once in the history of Mozilla, and it was paid for by Mozilla itself, because it's a huge task.
Mozilla needs reform as an institution, it needs new leadership. But its raison d'être is still very much there.