I don´t think it would be that viable at all. It would be really cool if you could just pull out your knife and throw it to distract or kill somebody, but considering that they wouldn´t one or two hit kill it would be pretty underwhelming. It would make more sense to add throwing knifes as a consumable. It could be really viable for disarming traps but I´m not to sure if somebody would be happy to sacrifice his legendary knife because he doesn´t want to shoot the trap.