In ArmA 2 we had a very nice and useful script that would cache AI units beyond a certain pre-defined range to increase performance.
http://www.armaholic.com/page.php?id=10102&highlight=CACHE
That script was not perfect and did have some issues, but it would be very nice to have something like this as a module in the editor. Specially with heavy loaded missions with a lot of AI on different locations it can help to reduce the stress the AI is causing.
For the ones that don´t know the script I am talking about, it basically un-renders all AI units in a group except the group leader from a certain distance of the player.
I have used it in ArmA2 in missions and it definitely made a difference.
Just throwing the ball up!