Well you can split all the hairs you like, and argue all the reason why the way you always did it is the only way to do it, but you know what? It's not going to change a thing. And, if any of those "well-rested" arguments of your held any water, I can assure you that the APA would have used them years ago. Yet, a much larger pilot force that LUS has lived with FCFS for a long time.
Don't try to add flight attendants or gate agents or ticket counter agents to that mix because we are not allowed the luxury of calling in fatigued. (And, don't you think your grasping a little hard if the best you can do is come up with a gate agent's sleep pattern disruption. Please. It is hard to imagine how little any agency cares about gate agents, or flight attendants, or baggage handlers.) Every time flight attendants try to bring up this issue to the FAA, the FAA appoints another committee to "study" the issue. There are no FAA rest rules for flight attendants other than we can not fly 7 days straight. There must be a 24 hour break either at the end of the 6th day or during days 2-6 which just causes the 7-day test to start over.