The problem with the boarding process is luggage. What airlines should do would be to make a checked bag free, and charge for overhead-bin use. That will reduce the boarding time by reducing the time to find bin space and stow luggage.
I suspect that airlines don't have an option to try this, because they all have co-branded credit card deals and frequent flier programs where some of the perks are free checked bags. I imagine that their credit card partners would not be happy about them devaluing the card by removing bag fees.
Also they won't do this because business flyers usually don't check bags. That way they won't be lost (by the airline) and so control over their destiny is retained by the flyer. I've done quite a few international trips, even week long trips, without checked luggage. Having your luggage get lost can be a real time consuming hassle and one you don't want to deal with when on a business trip.
I suspect that airlines don't have an option to try this, because they all have co-branded credit card deals and frequent flier programs where some of the perks are free checked bags. I imagine that their credit card partners would not be happy about them devaluing the card by removing bag fees.