I would put the user first, make privacy the #1 priority, make it plain to the EU that FireFox is the
only browser that can make that guarantee and long term stand by it and apply for subsidy as well as promotion by the EU and/or anti-trust action against Google, Microsoft and Apple for not giving the users of their devices the option to install/run FireFox right out of the gate.
Ad blocking and tracker blocking would be a central item built into the browser from the get-go. I'd get rid of any and all telemetry unless explicitly opted-in to by the user.
I'd make sure that updates are going to be limited to security issues only and that any other feature changes or additions would always be optional rather than forced.
I'd ax each and every product that is not in line with that mission. Rust would be welcome to stay since it is now part of the future of the browser, but I'd spin it out as a separate entity with its own income stream based on a trademark of the name and set up a foundation around that.
The Rustaceans would be encouraged to create their own governance structure and Mozilla would be just another user of that product.
Oh, and I'd rename the company to FireFox Brower Inc.
As for mobile, I'm sure that there is room for firefox on mobile but first you'd have to convince Apple and Google that they are on the wrong path, a distraction that likely would not lead to a win in appreciable time.