Sorry if I'm posting something anyone's already asked. (did a few searches but could not come up with answer)

How locked am I by my class choice at character creation? I'm currently maining a CNJ with aims on WHM, but I would like to try my hand at tanking (PLD) or DDing (BLM, DRG) as well.

I know it's "just" to pick up the weapon of the other class, but since I've joined the Conjurer's Guild, will I be hindered in obtaining the souls for the other jobs I'm interested in besides WHM?