Slightly off topic and maybe Jeff will throw stones on me for suggesting, but:
When I think about spells and which game in the past had the greatest spell engine ever, I always just have one answer: dungeon master.
Spells worked in a completely different way there: You had to combine several symbols/hieroglyphs to cast a spell. If I remember correctly, it was like that:
The first symbol defined to power of the spell, from very weak (but easy to cast and not consuming much of your mana) to ultimately strong (but difficult to cast if you didn't have enough experience, and taking quite a lot of your mana).
The second symbol defined the base element (like fire, water, air...). Some spells just required the base element: For example the fire symbol created a magical torch.
The more complex spells required a third and some even a fourth symbol. So the fire symbol with the ray symbol would create a fireball, while the fire symbol with the shield symbol would create some kind of fire shield.
So you could find very powerful spells by just trying the combinations or by discovering spell scrolls during the game. Theoretically one could cast very powerful spells on a very weak level pretty much at the beginning of the game, but with gained experience you could cast stronger and more devastating versions of the spell later on.
I remember having a sheet of paper next to my computer where I wrote down all the combinations that I found. Oh, and there were wonderful spells like "see through walls" or "show my footprints so I won't explore the same corner twice".
I'd love to see something like that back again.