I think it would make a lot of sense as a Perk. I don't like auto aim in some situations, especially when trying to pick out a single target among many. BUT if you are aiming at one target who is moving, it would make sense for a character with a high skill to automatically follow them better than what the player can do with their controls, it reinforces the RPG aspect. You can't translate mastery of archery, which is as much feeling as it is technical skill, as simply doing more damage.
I also have always thought there should be a circular reticle for ranged weapons. Lower the skill, larger the reticle, closer you have to be for an accurate shot.
Also; increasing the speed at which you fully draw your bow, ability to hold the bow steady longer (IF there's a limit to begin with, which there should be) maybe auto correct for wind and drop. That may get confusing because you'd have to tell the player to no longer aim above far away targets, which most people know to do, but once again, allowing "less realistic" actions that still result in success show how character skill is more important than player skill.