Spell obstacles currently serve three purposes.
(1) To determine the spell dareficulty and tax.
(2) To determine the spells effectiveness.
(3) To determine if it was properly cast at all.
Regarding Spells as Weapons under Advantage and Disadvantage (BWG page 514) we re instructed that “Disadvantage increases the casting obstacle.”
That can easily mean a Shards spell vs. Knife could get you a +3 Ob if you lose the advantage. Turning your Ob2 spell into an Ob5 which could cause a mage all sorts of trouble.
Under this system, “Combat Spells” are treated just like any other weapon or combat skill, and suffer the same penalties but those penalties do not effect spell tax or casting success. Only whether or not you hit your target, and if so, how well.
In the Shards example you would need 2 successes to avoid spell failure, but 5 successes to hit your opponent. Any successes over 5 could be used in the normal BWG way.
This cuts way down on Garbled Transmissions and Unwanted Summonings while allowing for some great cinematic moments as shards explode behind the charging hero and lightning bolts crash into rocks and trees.
Obviously, this only conerns combat induced obstacles rather than caster induced ones. So things like casting quickly or while injured would still go against your spell and tax obstacles as normal.
Note: The base obstacle to hit is already counted in the spell obstacle (or so I've been told).
This is the way we always played, I just found outit was “wrong” yesterday so I put it to you as the hack that it is. Enjoy!