Here are two ways that Mozilla could have a lot of impact: - If it is indeed too challenging for Firefox to compete against Chrome with a separate browser, there might be value in Mozilla maintaining an open-source fork of Chrome. This would allow Mozilla to borrow the good bits of Chrome for relatively low effort, and focus development effort on the the things that Google might not value so much (e.g privacy). It wo…
As for an open source clone of Android, it already exists and it's called Replicant. Mozilla already tried the mobile OS thing and failed. Not sure why you think they would suddenly have success. It's all about ecosystems in the mobile space and Mozilla doesn't have it nor will they ever.