I'm pretty sure with the latest patch on PC they unlocked more of the keys for remapping on the keyboard in the Options menu. Either way though for 100% remapping, you'll have to change the keys within the BaseInput.ini file at this location:
ProgramFiles(x86)/Steam/SteamApps/Common/FableAnniversary/Engine/Config/BaseInput.ini
In the BaseInput.ini file the section for keyboard is the "--- General bindings" section. Should be as simple as renaming the button entries that are in quotations to whatever you desire so for example "F4" = Exit, and instead should be able to change it to "F8" = Exit, and so on.
Make sure you backup the file just in case (though Steam can easily restore it if you screw it up anyway). Honestly the process is pretty annoying which is why I just play with an Xbox controller instead. Hope this helped.