you're lost in the weeds.
If AA mainline employees ground handle other carriers, then the number of employees that are allocated to work other carriers including regionals, may well not be adjusted to reflect who handles what carrier.
This is not about DL models. It is about the way airlines report to the DOT ON A MACRO LEVEL.
Airlines including AA, break out the number of mainline employees by work group and traffic statistics are also reported by operating carrier.
The percentage of seats and ASMs offered on each carrier's system by regional carriers is known.
The only point your argument proves is that AA and UA have higher percentages of their systems that are operated by regional carriers, including much higher numbers of flights operated by 50 seat aircraft.
So, yes, if AA and UA are "overstaffed" because they use mainline employees to ground handle 50 seat aircraft, then their staffing numbers are going to be higher.
Regardless of the model, it doesn't take a rocket scientist to realize that other carriers that have more efficient operations by using all mainline (such as WN) or larger aircraft even when regional carriers are included (DL) are going to have a staffing cost advantage.
Again, the point is still that AA employees can only expect to see pay raises if AA becomes more efficient in its staffing. Granted, those are largely mgmt. decisions but if AA has to pay mainline employees to work large numbers of 50 seat aircraft, their efficiency will be less.
More efficient staffing will result in a greater ability for the company to increase salaries.
Airlines will all spend similar percentages on labor to their peers or drive to that goal unless labor can demonstrate why it deserves higher salaries.