Well, you might give PRIDE a look. It’s close to your ideal in several ways.
A mage begins each turn with a certain amount of power, typically a d16 or a d20. Each spell has a difficulty level, from 3 (easy) to 10 (hard). The mage chooses his spell and rolls his power die. If the total exceeds the difficulty, the spell works. If the die roll ties or is below the difficulty the spell fails. IF THE DIE ROLL IS A MAXIMUM (e.g. a 20 on a d20 or a 16 on a d16) then the spell works but the mage has suffered a brainburn; his turn ends and next turn his power die is reduced a level (e.g. starting at a 612 instead of a d16).
A mage can attempt a second spell if his first one worked, but is now tiring and rolls a smaller die: d20 to d16 to d12 to d10 to d8 to d6 to d4. He can cast multiple spells until he fails one, but at increasing odds of a brainburn.
So choosing between powerful hard spells and easy/weak ones is important, as is knowing when to stop.
A mage can choose, instead of attempting to cast a spell of his own, to BLOCK an enemy spell; he rolls his die (and still risks a brainburn) and subtracts half the roll from an opponent’s roll.
Or he can BOOST an opponents by ADDING half his roll to an enemy roll, which might empower what would otherwise be a failure into succeeding, but also sharply incresases the odds that the opponent’s augmented roll is too high and so becomes a brainburn.
Spell lists have a lot of similar generic spells, but also many that are unique to cultures or philosophies. The hyena folk worship Entropy, for example, and have lots of bad luck and Murphy’s Law spells.
Spells (including Boost and Block) are cast simultaneously using cards.
There’s also illusions, divine pagan magic (Thor has his lightning), undead nihilism, Godfearers (ethical monotheists) Gifts, dwarven rune magic, etc. It is pretty customizable but not very generic. We start with the minis and then describe a culture, and then decide on spells that make sense within it. The points system works pretty well, and e.g two weaker spells users have advantages as well as disadvantages agiainst a single stronger mage who costs the same points. (The weaker guys have a harder time casting the powerful spells but are actually stronger on defense, blocking enemy spells.)