I believe a nice boost to ranged dps, to help bring them closer to melee dps, would be applying the attack / damage properties of arrows and not have these bonuses go on "whichever is higher".
It doesn't seem too far fetched to me to gain +5 to hit and damage from a +5 bow and also another +5 to hit and damage from a +5 arrow. Both items are seperate entities carrying their own magical properties, or in the case of arcane archer conjured arrows, you have imbued the arrow with these properties.
This would serve a number of purposes.
Allow rangers a lower dex and higher strength to pick up their dps a little as their chance to hit is going up. One of the main problems with ranger was that it's dps was so poor that you needed to hit with every arrow.
Give a use to the Arcane Archer conjured +5 arrows. What's the point of being able to conjure +5 arrows if you are using a green steel.
A nice boost to dps for the ranger that i believe, as conjured arrows or even the ability to purchase higher + arrows.
i think this would be a change that isn't drastic by any means and will greatly improve ranged viability without a lot of extra code.