Thats exactly what would happen. We once had the ability on the shuttle to have any deadheading or commuting pilot replace you on your last leg back to LGA. This was enormously useful as there was almost always someone available and could get you home when a commute from LGA would not be possible later. Then a brilliant pilot replaced someone and demanded the 5 hour daily minimum pay. The policy died almost immediately. There were hopes to extend it system wide.