I think this would be a great addition to TES games. Morrowind had it, but not necessarily exactly how Morrowind did it. It makes sense that as a novice mage, you would fail to cast certain spells. More so in the heat of combat. Then as you became better with a particular type of spell or magic type, you could successfully cast it in all types of situations, with a Master hardly ever failing even the most difficult spells.
At very low levels a novice could even mess up a spell, for example a novice of conjuration could summon an aggressive minion or a novice of destruction could set himself on fire? Or instead of make oneself invisible, a novice might make himself bright green or something ridiculous?
I just think it would add more depth to the magic system. Thoughts?