1) become absolutely trustworthy again 2) become the power user's choice again
To me, 1) means absolute control over updates and network connections. Become the antithesis to the patronizing "Ask me again later" school of thought which has become so sickeningly widespread over the last few years, and instead accept that "no means no", whether you disagree or not.
And I don't have to mention "partnerships" with entities like Cliqz or sneaky downloads of marketing extensions.
2) - Firefox tried to appeal to average users and failed, losing a lot of what made it appealing to the power users and evangelists in the process. Reversing that will be painful, because it means allowing people to shoot themselves in the foot, and accepting that some people will do that occasionally.
Making a useful power user browser means accepting that a lot of its value will be created by other people, and supporting that with a deep and comprehensive extension system, instead of clinging to Googles table scraps. Having a useful extension system also means the ability to install from any source I want, no Ifs and Buts.
All of these are risky. Useful tools often are. Give Firefox back its USP and a reason to exist, because "it's not Blink" on its own simply isn't good enough... even if maybe it should.