I posted earlier that a friend DM uses an actual unit (which he calls a spell-unit) dedicated to the mage's (or priest's) service.... a small retinue of magicians/acolytes etc, a cook, some bodyguards, some helppers, some brewers etc etc etc... i had posted a bit more about it in this thread or the other thread regarding this topic...

If the unit is lost, the mage cannot cast any more spells... Plus, if his unit is killed, he might be killed as well! It would make mages less willing to participate in a battle.

And in reply to irdeggman, i think, no, it is not like having a feat. The mage could be casting standard spells, battle spells, spells with a feat or whatever. The idea does not get involved with the way that the magic is cast. 2nd ed book explictly ssaid that a battle spell needs help to be cast and the "spell-unit" is the help.