Having a few rare, forgotten spells only accessible via scrolls would be nice, though I'm not fond of requirements on scrolls. Because without these requirements, your proposition just entirely makes the mage class/tree useless, as one'd better put all his points in warrior stats since he gets all the mage stuff with scrolls.
Also a major difference with regeants is that spells use several different reagents, forcing the player to make a choice between which spells he'll use or which potion he'll craft.
But in the end, it doesn't have to be a binary choice between the complicated version and the dumbed down one, both could be implemented and supplement each other: Player who find it too complicated to understand the system could buy potions or scrolls from vendors, while those who put the time and effort to store the reagents for their spells and craft their own potions would be rewarded for doing so.
