By far the slowest aspect of boarding is all the people with ever larger roller bags. And the fight for overhead bin space... And then figuring out how to check bags when in th end there isn't enough bin space.

The whole line of people have to wait while people try to find bin space .

So what if you did "anyone without a roller bag can board first". If you can just walk down the aisle and sit down you go first. You could then load maybe half the plane quickly and efficiently.

The let on people who have the roller bags. Let everyone else watch the fight for bin space from their seat rather than trapped in line behind the person trying to fit their expanded roller bag that is 19 inches deep make it fit in a 16in tall bin!!