Perhaps instead there should be weapons that are the opposite of 'unbalanced'. Balanced weapons would just swing at regular speeds but won't do as much damage. Feinting and such with them would be easier because the center of mass is closer to the grip. Then we can make weapons that simply aren't 'balanced' (I.E. the way they are now, without any modifier) to be slightly more difficult to feint with than they are now and deal normal damage. Then we have the current 'unbalanced' weapons which deal more damage and are harder to feint with.
The thing with different swings with a str vs. agi thing doesn't make too much sense, unless you made weapons specifically designed to be agile like a rapier or something. A strong person can heft and swing weapons around easier than somebody who isn't strong, regardless of what weapon it is and regardless of what part of the swing they're at. Agility in gameplay terms also refers to expertise (WPF) which is different from the ability to heft weapons around. It's just... abstracted... a lot, because of gameplay limitations.
For example, two people wield a mace. One person is strong, so he can swing that fucker really hard and bash skulls in (power strike). The other person is not quite as strong, but he knows how to use his entire body and positioning to put more weight into the swing and thus not swing like a bitch (WPF). Of course, mostly abstracted for gameplay.
As you can see I've put most of my WPF into talking out my ass, but I was never good with words =p
