Aww, I thought the bigger hit spread was a good mechanic. Oh well.
Abstracting can help, but you still aren't safe! Consider the super-intelligent but weak wisdom wizard. Such a person might be phenomenal at figuring out how to cast complex spells but wouldn't be very wise about what spell to cast or even learn in the first place. However, taking away the player's ability to pick what spells to cast would be horrible. I think you're basically stuck just using Int/Wis for use in spells and some dialog choices. Or are there other ways to bring brain-stats into play without ruining the game?