I would like for Fallen Enchantress to have more spells than Master of Magic, because frankly there hasnt been one game made since its release that has surpassed what Microprose did all those years ago.
For instance one of the coolest things about that game is that actually changed the environment.
Also there were some really nice BIG game changing spells like Timestop, Armaggedon or the one that dispelled all the spells that other wizards tried to cast.
Not to mention that each spell branch had its own flavor and they tended to balance each other out.
So please do the same with elemental. For inspiration a good idea would be to go through a few Magic the Gathering cards and get your inspiration there.