Make it easy to select which standard bar must be displayed and in what sequence. Now this is difficult and unclear using Settings or userChrome.css. You can improve this e.g. to allow to drag and drop the bars or to switch them on or off with the mouse.
A clear definition of the names would also help: 1) the title bar(<website> - Mozilla Firefox) in Windows style. 2) the edit bar (File, Edit, History, Bookmarks…). 3) the tool bar (customised: eg. with icons Home, Go back, Go forward, Reload, Show Sidebars, Download, Print…). 4) the browser tabs bar containing the open tabs containing a website page.