Kap is useless outside of the pistol, Chip has already hit Kap's ceiling running a gimmick offense last season, you can't win games but he might be able to take care of the ball scrambling a bit and hit the occasional first read or get sacked, he's like 30th in air yards, for the kind of arm he has it's shocking, extremely poor mechanics, very show windup, bad footwork, and he almost never throws with a flick of the wrist, absolutely zero touch, he's like the anti-Romo.
For a backup he would have to play in a regular behind the centre pro style offense, something he's proven to be incapable of.