Bro... All you gotta do is slip the sound guy a 20 and tell him to make the singer's guitar sound as bad as humanly possible... The gig will go bad, and piss off the rest of the guys in the band... Then all you got to do is stand in the back, raise your hand, clear your throat and say " Hey guys... I can play lead.... "
:)

Seriously... If it's an ego trip you want... Sounds like you are going to have one hell of a ride with him... If he is good at both, then hell sit in the back, hit those chords and collect that paycheck, all the time reminding the singer that it doesn't matter how much $hit he is doing in the band, the fee gets split EVENLY....