I tend to player my RDM as a jack-of-all-trade. I actually run around carrying a bow and arrow, plus some throwing items. My suggestion is to create a new /ja that grants RDM's the ability to have "magic arrows" in the ammo slot at the cost of a % of mp pool, similar to "diabolical eye"(DRK).
Once a RDM player activates this ability, their mp pool drops by say 10-15%. Duration could be 1min(3min with composure). The "magic arrows" damage could be scaled to either Divine or enfeeble skill level or just a set damage(moderate). Being magical in nature, they have no add delay only what the bow itself gives.
I would also suggest that this job ability be low enough so that subbing RDM would give rangers and other classes this "free arrow" option.