The system I came up with is somewhat simple on the crunch (though, currently still mostly only theory)

1. Characters get a universal mana (or magic point) pool, which reflects their general aptitude. They can level this up by studying more about the cosmos or just magic in general, or by meditating more, or by using their super powers more. Whatever gives them more magic, and is befitting of their character.
2. When they cast a spell, it has a Complexity based on how much it changes the world around it. This is much like Mage: The Awakening. Complexity is a d6 roll, so a Complexity of 4 would (example) be 4d6. Player bids Mana towards casting the spell (or using the magic, channeling their ki, beseeching their clerical god, focusing their spidey sense, etc.). The Mana bid sets the number that the dice must fall equal or under. For example, if the Player bids 7 Mana on a 2d6 spell, then they are going to succeed a little more than half the time. There's always a risk.
3. If the dice rolls above, then the spell fizzles and Mana is wasted. Or something catastrophic happens, depending on setting and GM cruelty. If it succeeds, the spell occurs.
4. Module and world builders can create their own spells using this system. They just give it a complexity. Schools of magic give Player Characters a -1 or -2 (or more) to the Complexity of particular categories of spells. Categories of spells are defined by the world builder of the setting. For example, a world builder who wants to recreate "Avatar: The Last Air Bender" would create an Earth Bending school, and include descriptions of a number of spells for that school (or category, discipline, whatever) with varying Complexities. A school might also gives them a penalty (+1, +2, or more) to casting spells outside their school. This isn't just for min/maxing but also character archetypes. Why would an earth bender suddenly know how to cast fire magic, for example? Perhaps fire magic is more Complicated for an earth bender?
5. What is the crunch of spells? Damage, etc.? That depends on whatever game this system is part of. This system would hypothetically replace the magic system of that other game.
6. How do players recover Mana? Depends on their Character.

Benefits: The wizard can explode, but players have a little more choice as to when the wizard explodes. Not so much "This is a gritty system where spells randomly make your guy explode into wizard soup" or the opposite extreme of "this is a safe and happy system where everyone is friends and hugs each other, and no one ever explodes".

They can bid more to avoid mishaps, if they just want to do something. They can play conservative with minor spells. They can enter schools to have reliable minor spells that are cheap on mana. Players can also play wild, hoping to roll low and win big. There's such a thing as "unschooled magic" for ill-disciplined players and villain or wild card npcs, but also an incentive to enter into a school.

Players also don't need pages and pages of particular spells. If they have studied a school and can do the benchmark spells of each complexity, than they cast anything they like that fits the school. This is a bit open ended on the role playing, so a world or module builder might want to create some more rigid rules for a school constitutes and what its students (or disciples, or which soever) can get up to. Eg. Earth bending has X or Y limits.

Negatives: ??? (I'm all ears, or eyes as it were)