I believe piercing weapons in general, and archery in particular, get short-changed in D&D (retro, clones, the whole smack). This is an off-the-cuff, thinking-out-loud idea to rectify that. Two ideas, actually.
#1) I Can Shoot a Gnat Out of the Air
On a successful hit, the player adds his margin of success to the damage roll. For example, if you need a 14 to hit, and roll a 17, the damage roll will receive a +3 bonus.
#2) Through the Heart
Damage rolls for piercing weapons explode. In other words, if the damage roll is a "6" roll again and add it to the "6". If that is a "6", roll and keep adding, until the roll is not a "6".
I wouldn't combine the two. If I were using the first one, I would strictly enforce range penalties. If I were using the second, I would employ the optional "Weapon vs AC" rule, at least with piercing weapons.