What are you afraid of? It makes magic too powerful?
Sounds like you're using lame Spells. They shouldn't be safe and reliable. Unleashing one should be a terrifying moment for all involved.
It doesn't have to involve horrible miscast tables and tacked-on Sanity systems.
Start with the Spells.
Sleep is one of the worst. Have it force everyone in range to save or sleep, including the caster!
Fireballs should engulf an explosively unpredictable area. Use it in open fields, or stand well back.
Magic Missile is might not give up after striking one target. It might fly around the room like a piranha, snapping at everyone it can reach before fizzling away.
Or better yet, throw away that d&d Spell list and imagine some uniquely magical creations.