Also, now that i think of it, I have no idea how scrolls will work now that we have spells equipped in a hand rather than in a "bonus slot." Could scrolls be abolished ala throwing weapons in favor of staves? Perhaps they'll be queued up in a spellcasting hand. One of the many thing I'd like to hear everyone' thoughts about.
Hmm, after giving it some thought:
Scrolls are basically potions, with the exception that the spell effects aren't limited to yourself only.
So I think it would be logical if you could write (enchant) scrolls with the same rules as making potions, but with different ingredients.
You need at least one arbitrarily rare ingredient and every enchant would also require magica, 2 or 4 times the casting cost of casting the spell normally (penalty reduces as you "enchant" skill improves).
More powerful scrolls require more of the ingredient needed to enchant scrolls.
All this is needed to prevent the skill to be overpowered.