Sadly it seems to go against the crossbow concept, to burst fire like that.
I had an idea for a feat that would specifically buff the usage of non-special bolts, as a counter to the kinda mindless "Special Tactics" feat that buffs special bolts very directly, it would be called Mad Notching or something, would prevent you from using special bolts while the buff was active, and it would reduce accuracy at range but lower your firing AP cost and increase your critical chance, making it so you had an option besides going from A->B, where A is use Snipe/Aimed Shot and B is use special bolts, typically Shock ones.