Might try something based on swordsmanship, as long as I can find a way to avoid making it feel too close to Demon Slayer

Oh man, I thought about this 5 minutes after I left, and you said you want your character to control paper—a power system based on Arts and Crafts. The users are kids whose parents are supernatural beings, and their unstable, still-developing powers become Craft Tricks. Its Rugrats meet Naruto, and you OC could use Papier-mâché based abilities.

That was before I made Weight of Words. I made a character that turned the ability to create and control paper into something surprisingly powerful. Even for individual OCs, I haven't found a power idea interesting enough.

Have you tried combining your power systems together?

Sort of. In Weight of Words, I included the possibility of people with weaker/non-physical abilities getting to pseudo-superhuman levels via training, and martial arts were included in that too, just not as the main point.

Maybe try a power system with a theme based on swordsmanship or weapon-wielding in general?

Considered that (and sorta still considering it) but I'd likely need to find a way to put all kinds of weapons into the same world. All kinds of medieval and ancient weapons fell out of use when guns started becoming more common and easier to use, and I'd rather not have to exclude a pretty broad type of weapon to make sure that all others can still be used.

So you want guns and weapons in the same world?

Yeah. The goal is for guns to be another type of weapon, like blades and polearms.

How about a power system based on gods/deities of myths/pantheons?