Yes, I do realize that followers will equip their (in most cases) standard Hunter's Bow in order to have unlimited ammo (arrows). This is what's blocking the followers from equipping any far superior bow you might give them.

This issue has yet to be resolved.

Followers should be able to use the best bow they are given as long as they are given a steady supply of arrows. They should only revert back to the Hunter's Bow when they're "out of ammo". When I give Lydia 500 + Ebony Arrows (or any other type of arrows for that matter) and an excellent Ebony Bow, it really annoys me that she still pulls out her Hunter's Bow. It then takes ages for her to dispose of enemies at range.

Please, Bethesda. For the love of God, do something about this.