The fcfs way of handling boarding in my opinion is outdated. When most airlines instituted this rule, the intent was to let whoever had been waiting the longest at the airport for the flight to be the first on....It was like standing in line for a movie, or concert or anything else. And it made sense...With today's technology, we do not go down at stand in line at the airport anymore....we check in at a computer terminal and anybody can check in 24 hrs in advance and then go about their other duties for the day. It's not like you sacrificed for that advantage by hanging out at the airport all day like in the old days.
Boarding by seniority makes more sense and provides a well deserved advantage if you have sacrificed 30 years of your life for the airline as opposed to 1 or 2. The airline can provide each employee a few higher status boardings each year for your vacations. US uses the SA1P. That way, a new employee can select when it is important to have an advantage for vacations or when he has more important travel.
I would not be opposed to a fcfs policy if we require you to check in at the airport. That way, only those who really need or want to travel will be motivated to make the sacrifice to go early.