rRandom
If John doesn't know anything about the person he's replacing then that's a big risk, it would've been better to have the spies gather Intel on someone they deemed suitable so he would have the requisite information(friends, family, etc.) to pretend to be that person or just replace a spy. Though he could use the skirmish to sneak in first then meet up with the spies to enact this plan. Also what's he gonna do if they send him out to fight the heavenly lightning sect? The vice sect leader and sect leader shouldn't be so dumb as to ignore these issues.