Probably say smart spell use and have each one with a lantern make some kind of save to avoid their light going out most likely. I have AoE affect items that would be affected. Don't fireball the guy you want to get a scroll or potions off of, heck be careful fireballing the heck out of the guy whose metal armor you want to get later. 1e had it a lot better, if you cast devastating AoE spells on people you might ruin their stuff with all that energy that is burning them to death for example. So if you see a guy that is running away with arms full of sweet spell books you can't fireball him and then hes a burn mark on the floor with all these pristine books laying around him. If its a spell that only effects the person but for some reason has no affect on anything he is wearing or carrying, well to me that's just ridiculous unless its some kind of effect that wouldn't burn, freeze etc. Might as well have AoE spells not affect non-enemies so you can just drop them willy nilly and never worry about friendly fire. In the end I just ignore rules that I find stupid and go with what makes sense.