If you can pull this off pleiadian, you will be officially declared my hero and I will consider renaming all Coriolis stations to Pleiadian in my install of the game. This should give a hint of the order of magnitude of the project you are about to undertake.
Firstly, the UI code is very particular. It has a few nice parts and I like some of the ideas I see in it, but overall it is very convoluted and very difficult to use. You will soon find that out for yourself
. Just changing the layout of existing screens can be a good challenge. Secondly, the design of the UI is such that the game recognizes one active screen at a time and adjusts its behaviour and controls according to which screen it is shown. So, your F9 proposal for example, would have to take into account how to handle the cursor keys while displaying the market screen or the short range chart or how it would handle key input in general when viewing the long range chart in planet search mode.
I think that basically we are talking about a full rewrite of a major part of the game here, exactly because the UI is designed from its roots to be like the old Elite. In addition to the files suggested by phkb, I would think that extensive changes to PlayerEntityControls.m, Universe.m, maybe core JS scripts that handle gui screen changes and probably a bunch of other files will be needed. It is doable for sure, but at a large cost in time and frustration.
Good luck and we can help if we can, but remember: it's hard.