Please do not lock Jobs to the Weapon Class that unlocks them.

[SuzakuCMX]

Unless they implement 1 handed crossbows you won't even have to address this issue.

Several jobs in FFIV used bows and arrows (WHM, PLD, SMN I think) which did not affect their ability to play their role. But to take the paladin example, if you're not able to equip a shield because you are playing with a 2 hands bow, you reject a whole set of shield specific defensive abilities that probably will not make you a desirable paladin in a pt, but that could make a decent and fun combination for solo or specific roles, as pulling and crowd control idk.

I'm pretty sure you can at least use a buckler with a bow.