Something else to consider is the magick system. The runes came in three classes: nouns, verbs, and adverbs. The verbs all took a direct objects (the subject of the magickal "sentence" was always 'I'). The adverbs were either the god runes or the pargon rune. Just imagine how much they could expand this system. For instance, verbs that don't take a direct object (like "float," "grow," or "move"). Or maybe giving some verbs the ability to take verbs as objects (like adding spell casting enemies, and then you could "protect" from other spells). You could also expand the adverbs, or even add adjectives (with things like "for a long time," "briefly," "far away," "small," "quickly," etc.). Last, but certainly not least, they could make runes that are impossible to memorize (because they are constantly shifting in appearance), and expire after one use. I know that ED's whole system was never based on a scarcity model, but this is one way they could alleviate the fact that regenerating MP made the game too easy (say, make healing spells too slow to use in combat without a "quickly" rune, and make "quickly" runes one timers).
BlackGriffen