If I were assigning keyboard shortcuts to styles, I would probably use the ability to set up sequential keyboard shortcuts. I would use something like Alt+Shift+S as a trigger, to be followed by a letter or number for the particular style. So, for instance, I would set Alt+Shift+S,S for the Strong style, and Alt+Shift+S,E for the Emphasis style. That is, you press Alt+Shift+S followed by the letter S or E.