I haven't set this up yet (mainly because my guys are too small to have to worry with it thusfar), but my thinking on it was to simply have a macro set on F keys to automatically switch focus to my primary and secondary (and tertiary if I see a need for it).

For example, my priest dies (primary, which was set with f10 which is a macro on all 5 toons that sets focus to the priest). I hit F9 which changes the focus of all toons to my mage1. Mage1 is setup with different movement keys than any of the other toons (for me, my red shift and direction keys on my nostromo). This allows me to continue moving the group (to get out of dodge most likely) and to keep on casting (as long as focus /assists and everything are coded in all my macros).

So basically, I hit 1 key and shift my view to another monitor and I'm back in business. When I enter the game I hit 1 key to set my group's focus. That's as simple as I can think of.