I think it could be nice if friendly fire / no friendly fire was a property of the spells or the spellcaster. So you could have a spellcaster who has a 50% chance of not inflicting friendly fire, or you have a spell that is way less powerful than the normal version, but doesn't inflict friendly fire. So if you don't like friendly fire, just use your not-so-powerful spells.
The thing with just turning it on/off is it makes the game WAY less difficult (in general, don't know about this particular game). You have this death ray spell that shoots out in a cone. If you are hit with this, you die. You are in a heated battle with everyone lumped together in a small area. There are 10 enemies versus 3 of you. No friendly fire: just use your death ray. Friendly fire: You could just use your death ray, but then you'll kill two of your characters as well, and the enemies might not be affected by it. What to do, what to do...
