Modernized katar would be amazing as one-handed weapon for martial artists.
BUT KATARS COULD BE CONSIDERED SHORT BLADES!
No, not really. A knife has a small handle that requires to be held, you use your whole hand and forearm to wield a katar, or both.
However, there are other one-handed martial art weapons that can be used, for example..
As you can see, chain whips can be used in both hands,and the wielder is extremely agile at using them.
As you can see, they're blunt, but sometimes the tips can be narrowed into deadly points for the sake of penetration. They're focused on deflecting weapons, or set them aside with multiple strikes. Since they're not sharp, they cannot be considered blades.
Or, at the very least, make brass knuckles work with martial arts as well, maybe? So that new weapons won't need to be added, and the existing weapons can be tweaked slightly to scale off brawling or martial arts