Another interesting way to increase the number of shortcuts is to allow multi-key shortcut sequences (e.g. F, I for Fillet). FreeCAD implemented this with a user specifiable delay in ms. The command is activated if no other key was pressed during the specified time window in ms.
Basically, you can use single key shortcuts, shortcuts with all modifier combinations and any combination thereof (e.g. something random for illustration sake: F, Ctrl + I, Alt + F2, Shift F Or just F, F Or F, Spacebar + F Or T, R, I, M). This is very flexible and helps people who are used to aliases (Autocad or shortcuts like Revit). The one system to do everything you want.