unfortunately, adding more base items of "staff" type is possible but will surely cause item morphing. you're right saying they are hard to find with a suffix other than that of +some spell
in diablo 1.09 I ckearly remember that Adria was selling some staff with a suffix of battle type. it was quickness or something. Perhaps, Illusion will teach me how to do this here, too, if we can find that code there. Item generator should be modified anyway Screenshot below:
But it's not that bad actually, Monk's situation can be corrected by giving him higher base damage when wielding staff.
I'm also planning to give him (and Assassins) a critical damage of 4x (instead of standard 2x). This will give them +33% damage on average at Clvl50. Maybe make +100% damage vsDemons into +200% when used by Monk (Monks are supposed to be true Exorcists).
Damage formulas, edited this way could provide better balance for Monks. Just you wait. In the future we will make changes that others never thought possible. Along with a lot better difficulty balance. We really need time (and some help with easy but tedious work).