[Refplace]

If the goal is to use arrow skill instead of Innate Attack skill you could just change the spell. Instead of putting it on an arrow you draw the bow back, concentrate to cast and let fly. I dont see a balance problem if the spell has the same stats otherwise. Bow is harder than Innate Attack to learn and requires a bow to use which are drawbacks but the skill being more generally useful since it serves double duty is a nice tradeoff.

I'd allow them to add the bows ACC to hit as well. I do something similar to that with wands for my game where they add +1 ACC as a pointing device for spells cast through the wand.