Yesn't
I do understand the intention behind fatigue, and at first, like capture, actually liked it, but the more i played (wether in other hacks, runs or just thinking about it), the more i think there're are better ways to do what it tried to achieve
Controlling what units players can field is a big no-no for many players
In some chapters, some units are vital for events/recruitment - good luck if they are fatigued - Although S-drinks help with that, so it's not that big of a trouble
Funny enough, i think one of the reasons Thracia is so easy is because it has to account for fatigue - has to account for weak units and so enemy units are dead weak the whole game
You could achieve the player rotating units with a "reverse Fatigue". As much as a i dislike 3 Copes, it had this little something called "Enegized" Status, where 2 of your benched units get extra exp on their next deployment - maybe apply that to all units have been benched for more than 1 Map?
Just my 4 cents anyway