For years, I assumed that I could only a few keys in vi-the characters like v and A that aren't used. For instance, if I mapped F to do something else, I thought I'd lose that handy "forward one screen" command. You think the same thing? Then we're both wrong!
Just use the noremap option. Here's a simple example. You can make F the "show file information" (normally G ) command. Then, make A take over the "forward (ahead) one screen" function. Put these lines in your:
set noremap map F G map A F