Following on what you were saying - I understand the scrolls themselves are written in Draconic, Celestial, Netherese and Demonic - its not just a recipe written in common like making chicken soup. If you don't pronounce that shit right you may catch fire, explode, or be polymorphed into a slug - like rolling on the Wild Magic table but only negative outcomes.
Scrolls are "written in a mystical cipher," which may be Draconic+etc, sure. And I agree that it's dangerous if you get it wrong, but it's possible you get it right. The more familiar you are with mystical ciphers (arcana) and languages (intelligence), the higher chances of being able to pronounce it correctly.
So would you want a penalty (roll on a negative-only WM table) if you fail the arcana check to use a scroll? Or for simplicity, if the spell is harmful just have it go off in your face and if it's a buff spell (Bess), make it a negative effect (Bane).