Dear Mozilla team,
I'd like to strongly advocate designing Firefox as an application that fully adapts to users' needs, rather than users having to adapt their workflow to the application.
For me, this would be the most sensible approach, as the way browsers are used differs so greatly from person to person.
This means, besides the visual appearance:
Full optional customization of the user interface by choosing the elements and subelements, customization of hotkeys for everything, and provision of a variety of plugins (which is already given on the desktop).
It would also be good if plugins could access the entire Firefox user interface so that they could modify it.
This approach could also increase the popularity of Firefox, as it could fulfill (almost) all expectations of a browser by definition.
https://connect.mozilla.org/t5/ideas/customizeable-toolbar-on-android/idi-p/3126
https://connect.mozilla.org/t5/discussions/more-ui-customization-for-firefox-on-android/m-p/8396/hig...
https://connect.mozilla.org/t5/ideas/customizable-hotkeys/idi-p/4979