I like Wizards being able to learn spells from any scroll. It calls back to one of the few good parts of old DnD. I don't really think it's a problem balance wise, for a couple reasons.
1: Wizards pay heavily for that kind of advantage. With no armour proficiencies, not even simple weapon proficiency, and the smallest hit die, they're outdone in combat ability by any other class.
2: Most spells are honestly less good than Wizard spells anyway. With a couple exceptions, putting a Cleric or Warlock spell onto your prepared spells just means that you're not preparing the best spells you could be.
It would require rebalancing Sorcerers to be a bit better, but honestly, with the ability to swap prepared spells on the fly, Sorcerers are going to need help anyway.
