Ya, according to this survey about 22% of gamers are Storytellers, or perhaps "narrativists", who enjoy shaping the story. But 22% of gamers are Character Actors, who enjoy inhabiting the story, and to do that, you need a somewhat predefined world in which to explore.HOWEVER!, there is one big caveat. For many groups, you're going to want some specificity about your character's abilities beyond "whatever the DM deems appropriate." For me, for example, I would want a Fireball spell that had a specific effect ("creates a ball of fire") and a standard baseline costing/potency (say, it's a Daily), rather than a broadly defined "U DO MAJIK! DM SAYS WHAT HAPPENS" effect.
That requires more rules, which I, personally, am OK with. I'd rather have rules than be forced to make a hundred judgement calls in a night. Not every group falls into that camp, of course, which is why I'd still love for this to be an option.
I was wondering how "gritty" fireball rules would work, without being too complicated. I thought:
1) As a general rule of thumb, if a power reduces a PC to 0 hp, the PC suffers the full physical/biological effects ie., acid burns that require magical healing, burnt clothing and scorched armor from fire, etc.
2) If such a power does not reduce the PC to 0 hp, the PC has evaded the brunt of the damage (player may narrate accordingly) and takes no collateral damage.
3) If a PC is caught in an area effect with no partial cover and cannot evade with a 5' step (or move action by spending an action point), the PC cannot save for 1/2 damage, and takes collateral damage as if reduced to 0 hp (yet miraculously alive).
#1 models the "realism" baseline that fireballs, etc. kill and burn anyone and everything caught in the blast. #2 is based on the "realistic" genre convention that protagonists always manage to evade or find cover against fiery magic, dragon fire, etc. #3 is based on the "realistic" genre convention that I've never seen a protagonist take the full force of a fire blast and survive unscathed. #3 also makes pre-combat strategy vitally important, ie., never face a dragon on an open field, try to fight a dragon in an area with lots of partial cover (ruins, boulders, etc).