Even if Koy can only throw the ball 20 yards accurately, IF he can consistently make good reads, get the ball to the open receiver and not throw into double coverage because he is fixed on one receiver or rushing his reads, consistently moving the ball 10 to 20 yrs on a pass play will win games. All Koy would need is a bruiser running back with good vision who can punish LB's and DB's and someone who can be a change up speedy back and he would have the tools needed to move the chains consistently.
A team does not need 40 plus yard pass plays so long as the chains are moving consistently and first downs lead to touchdowns albeit 10 to 15 yards at time via the air.
I say give Koy a chance under center and let him show what he can do.