Speaking as a former counter dragon, it would make things 100000x more efficient IF:
-> Preboarding: get them all lined up in the MAIN CABIN LINE. Get 100K/MM/First in the priority line.
As the PRIORITY lane is moving, the other agent at gate starts talking to the folks who need help, tagging strollers, etc. That way once the priority line is empty, they start moving in the pre-boards.
Venturi method used in boarding