This is a fine simulation, and, as described, it does not account for overhead baggage handling, and as mentioned in other comments: families traveling together.

If you have ever taken a commercial flight, you have seen it: the individual that needs two people to team up (or one highly capable one) and lift up or down their 40-50 lbs (~20 kg) roller from the overhead. Half the time, their help is in their party, but it slows things down.

I would estimate that this happens at least once every 4 rows on a fully occupied 6 seat wide aircraft.

Given this, forbidding passengers to bring carry ons aboard that they can't overhead lift themselves would be the only way to speed things up regardless of boarding/deboarding strategy.

Is that practical? Probably not.