it is possible to have a single Safarifox.jar to change all the settings "automatically" (a single installer to use on Firefox page's external installer) instead of having us replacing the file, which I think is the only thing you can improve there. However for the compact extension we do need to overwrite the original compact.jar from the user profile directory, as skin does not support extension.
Anyway, you instruction do let me know a lot more about firefox but customizing it have spent me a whole friggin day, and I'm still exploring the potential of userChrome.css. btw, the only thing i don't like about skin is that the font of menu and context menu and almost everything sucks, it's huge and big. I have to manipulate userChrome.css to change all back to my elegant lucida grande. I think you should use system font for you skin, then it won't show those stupid huge fonts.
As a conclusion, your skin rocks and keep up the good work. All of above just some comments I would like to give for you to improve. The skin itself ALREADY is awesome enough.