Why. Is. It. that web browsers seem to be built with the express and sole purpose of being as annoying as possible?
Nothing is truly "free". It ends up being a tool to sell you shit, track you to sell you shit later, and display as many ads as possible.
I get where you are coming from regarding screwy and ever-shifting browser UI's. I'd like to see a browser library that allows one to use the common programming languages to implement the general UI environment. The dev can program all the browser buttons, menus and panel layouts, but let library calls do the actual web-page rendering for the sub-panels. There'd be several demonstration configurations (layouts) to select and customize.
I'd like to see a kind of modernized version of Visual Basic classic. One could whip out a general layout in no-time with barely any code. However, it's probably not for the persnickety. Finding a happy medium is tricky, as being both newbie friendly and guru-friendly is tough as nails.
Mozilla tried to do something like this with XUL, but it sucked.