This is what happens on proper airlines
If the incoming crew flags an item, the station mechanic inspects, determines whether repairable/serviceable/unserviceable. Crew takes appropriate action.
If operating crew identifies an issue on boarding, the station mechanic inspects, determines whether repairable/serviceable/unserviceable. Crew takes appropriate action.
If a passenger identifies an issue, the station mechanic inspects, determines whether repairable/serviceable/unserviceable. Crew takes appropriate action.
"Appropriate action" in the case of an unserviceable i.e unsafe seat would be to reseat the passenger.
In the case of a full aircraft, someone gets off.....