Not talking about characters who already have established weapons like Jade and Kabal.
Nearly everyone in the 3D games were given weapons whether it actually fit them or not. Out of all the unconfirmed characters who don't have established weapons, who should have them if they return? I'm talking about making a weapon a major part of a character's identity, that they'd use during combos and/or specials and/or fatalities.
Kira's knives suited her superbly, but they're already Kano's thing, so I think she could be given Kobra's machete from MKA to differentiate her from him. I can't think of anyone else in the MK series more undeserving of such a fine weapon as Kobra.
Ashrah's blade, Darrius' gauntlets, Dairou's autumn dao, Frost's daggers, and Hsu Hao's sun-moons, are weapons that I think fit their respective users well.
Jarek's kick-axe from MKA is another that comes to mind, but primarily because it could be the butt of jokes, like other characters referring to him as "Lame-axe Jarek".
Kai's Gurkha Kukri from MK4, while I'm not sure it suits Kai himself, should certainly be given to somebody.
That's it for now.