
Roll Willpower, not Charisma, when using magic.
Me, five minutes ago
I wrote that. Then someone mentioned a method of magic I had forgotten: summoning.
Think of it like this: instead of casting spells in a fire-and-forget Vancian fashion, a “spell/spell slot” allows you to reach through the void to contact a spirit, elemental, or supernatural being.
It reminds me of World of Dungeons:
Most magic requires summoning a spirit, demon, or elemental to perform supernatural effects. A Wizard begins play with the occult knowledge to summon two spirits. A spirit has a name, an appearance, and two domains of power (flame, shadow, stone, lightning, secrets, fear, etc.). To summon a spirit you know, you require one of the following:
John Harper, being awesome.
-1 hour of uninterrupted ritual.
-A dose of quicksilver—a mild poison and addictive drug. (10s per use). If you drink more quicksilver doses in a day than your Level you must attempt to resist its negative effects with a CON roll.
-A magic item containing a bound spirit.
A Wizard may command a spirit to perform a single magical effect that falls within its domains.
It feels a bit like arcane Pokemon. Eventually a character may build up a team of spirits to contact, each with different traits to give the wizard a wider and wider pool of options as they level. Either they are able to summon spirits more often or summon a new spirit.

To add all sorts of flavor and preventing casters from all feeling the same, each being has their own method of being contacted, a way to compensated for their work, and unique traits.
Maybe the spirit is a greedy mermaid that requires a gold coin to be coaxed from their underwater residence. Maybe each task a bone-dry skeleton completes for you requires a touch of blood as payment, hoping to someday assume their old flesh. Maybe the imp can only be found in a mirrored surface or under a moonless sky.
Use this absolutely WILD table about “entities” from Coins and Scrolls to start.
Perhaps the monsters you find can become spirits when they pass on or engage in some sort of ritual with the wizard.

Implementing this into Electric Bastionland or Red Ink Adventures:
When you test’s a spirit’s patience by asking for too much or too many times, roll Charisma to avoid dire consequences.
Also roll Charisma if you don’t pay your dues to a spirit. They want what you promise them.
And that’s how you use Charisma for magic!
(Although Will/Willpower is a perfectly acceptable alternative in this case, in order to include Into the Odd and Maze Rats in the mix).
Again, here’s that random table from Coins and Scrolls. Check it out.