fighter weapon category change feat thingy

[JW063]

Can anyone help me? i am trying to make a feat that will add a fighter weapon category to a weapon that a character has weapon focus in. i am having a hell of a time trying to figure it out.

what i am specifically trying to do is have a scimitar treated as a weapon in the monk fighter weapon group.

i am pretty new to all this so any help anyone could provide would be super useful