I understand it would require a lot of revamping over the old system, such as how it would work in third person view, and if it would be incorporated onto consoles, but I can't help but think this would be a lot more immersive and make for a more rewarding combat system. Perhaps even make it an option.
Click the attack key (or button) to perform an automated slash. Hold down the key and drag the mouse to direct the slashes and perform combos, block oncoming attacks and make for some pretty awesome fencing/duelling style combat. Would even work with determining how far/strong the tug on a bow would be, and allow for more specific aim distance.
I understand this is all theoretical, but it just came to mind and I figured I'd put it out there for discussion.