Ideas on fatigue, elan, and attrition

I've tried from time to time to come up with a simple mechanic to reflect aspects of warfare such as fatigue and attrition. This seems particularly important in regard to troops such as Wb and Kn that relied for a great deal of their effectiveness on an initial furious charge.

The challenge for me has been coming up with a system that relies on mechanics already in the game -- competitive die rolls -- rather than pulling in new ones -- such as record keeping or using markers.

I was thinking of something like an army elan factor or die roll. Each army starts the battle, for instance, with a +5 Elan factor. In order to get the QK from Knights and Wb against heavy foot, an army must maintain its elan.

After each pair of bounds, both players roll their Elan die. If either side doubles the other, the loser no longer gets elan.

At +5 each, there is no risk of this -- a 1-6 would still be 6-11 modified. But, as each side loses elements, it's elan factor drops by 1 per element.

In addition, you could determine that every three bounds (or any other number you like) both sides lose one elan factor. So even if no elements are lost, both would roll at +4. This would make it possible to double up each other. Three bounds later both would drop to +3.

So elan doesn't just hurt Wb and Kn, you could say that subsequent loss have meaning.

First loss: Wb and Kn QK goes away.
Second loss: -1 pip per roll (1 minimum)
Third loss: -1 in all combat

Other systems could be created. And this would strictly be for scenarios or home games. I'm not suggesting anything for tournaments.

Do people have other ideas? My proposal is nearly off the top of my head, so I welcome constructive criticism.

JFM