Any 8 Int Fighter being able to cast Fireballs from scrolls is "harmless homebrew"? How about Blur and Mirror Image? Eldritch Knights will feel so special when any other Fighter can be a spellcaster too and steal their unique perks, while also using their own Battlemaster or Champion stuff the EK doesn't get.
Then there's simply making magic feel cheap and illogical in the setting when it's widely available to anyone regardless of class or stats. Those scrolls aren't written in english or common yet somehow everyone can read and speak the arcane language.
It's just a flavor and balance fail. You can multiclass a character into Wizard if you want that ability. It should at least require the Magic Initiate feat, as long as you have to roll those ability checks.
If you block the scrolls, you may as well remove them from the game.
The scrolls themselves are very limited in the game, I doubt if I found more than 2-3 of each scroll (I'm talking about the ones that actually make sense to use).
Due to the fact that the scrolls are disposable, they will run out quickly and unlike the Eldritch Knight, you will not refill them quickly.
