[Leech]

Ooh... Burrytar's post has just made me realize something else that might go to diversify magic, make it interesting, make it zaz-filled...

Genes!
Randomly generated gene pools which are not shown to the player.
Then, you have magic be a very large system... and only people with certain wittle genes could do this branch successfully, or would gravitate towards it, ect...

Very rough system, but alas, it's a system.