I've always wondered why you couldn't scribe spells in these games. You come across magical scrolls, but never can make them. In the past you could create magic, but scrolls usually have the most unique spells. So why not have the ability to actually write magical scrolls? Obviously you would need a couple things...rolls of paper, inkwell, feather. You can't simply just write a scroll though, it has to be imbued with a magical essence related to the spell you're writing. So like alchemy or smithing, you need the right materials.
What materials? Rare elemental materials, (element) salts, stuff like that. Though any one scroll should have a rare piece to it, that spawns once every...30-60 days? Maybe two rare pieces for the best spells.
Just think it would add a great twist to crafting without making any character overly powerful because these scrolls for 1.) are not found that easily, and 2.) can't be made very often.