I'm just gonna tell you what i think SE might do with weapons for the new jobs.
I think they'll probably make it an ability on your action bar like say if i was on Mrd and maybe they'll make it Dark knight i would have to put (Scythe: Cost :3) into my Mrd action bar to use the Dark Knights weapon. or they might just make an action spot that just says (Dark Knight: Cost 3) which will include Scythe wielding. and then after that whatever abilities comes with the job would cost more