Vacations , replacement , sick times.... you can always use an alternate. Bass player can't make it..
3 guitars is not too much... acoustic guitar, electric rhythm, lead.
Played in worship band with 3 guitars and it sounded great. Had a Lead player who could not play rhythm, I played rhythm electric and there was an acoustic rhythm.. When the lead player could not make it , I stepped up to the plate (with my tele) and played lead. I also subbed with bass.