If you use keyclone you could make a keymap that does something like F1 -> F

On the F1 key bind the macro for jamba

/jamba setmeasleader

On the F key bind the macro

/follow party1 or /assist party1

Now whatever window has focus will become the leader, and the others will get the command to follow or assist the party leader. You obvioulsy have all the other targetting business figured out so that should be all you need. his setup will be identical for every character. It also frees up the F2 and F3 keys for you.