Why, make a browser that is lighter, faster, and more privacy focused. And with excellent support for plugin developers. Let the bells and whistles be plugins developed by third parties.
Chrome is the product of a company whose mandate is extracting as much data as possible from its users to feed their ad business. Firefox can and should be better, as they could be 100% user focused.
A Chrome monopoly in the browser space has the potential to be more damaging to the web than the Microsoft monopoly in days gone by. They want to make the world a better place? Well, they could have made the web a better place, if they could meaningfully take some share away from Chrome.
It's going to be hard, almost impossible, to be faster than chrome, with the huge amount of money and man-power Google can throw at things. They can probably get "lighter" (as in support fewer things), but I don't think that's going to make things any faster.
Also, experience tells us that being fast and light is incompatible with excellent plugin support, as the more hooks you provide for plugins, the less you can change without breaking those plugins -- that was Firefox's previous problem.
Google's main focus is in extracting rent from their dominance, not in making the browser faster, lighter or whatever.
As for plugin support, that's the challenge no? Make it so the contract for third party plugins can be maintained without breaking them every 6 months as the browser improves.
Firefox has excellent developers. The fact that it still has some relevance despite many years of mismanagement is testament to that. I bet if the company behind the browser was laser focused in making it as good as possible, with no compromise, they could challenge Chrome dominant position.
Chrome is the product of a company whose mandate is extracting as much data as possible from its users to feed their ad business. Firefox can and should be better, as they could be 100% user focused.
A Chrome monopoly in the browser space has the potential to be more damaging to the web than the Microsoft monopoly in days gone by. They want to make the world a better place? Well, they could have made the web a better place, if they could meaningfully take some share away from Chrome.