The solution is not as complicated as it appears. Having previously worked as an agent at LHR for years, the delays and frustration for boarding arose due to the amount of carry on luggage allowed onto the aircraft. ITs that simple! Nobody monitors this anymore, and waiting until passengers arrive at the gate to insist bags are checked into the hold just causes chaos and fights. If hand luggage is monitored at checkin in with the 7kg limit reinstated, people are boarded much quicker. Yep, dont overcomplicate things......board those needing assistance & FFs with higher status first, then the remaining passengers according to rear first (if theres only one door) or middle first if there are doors front and rear. Its logical. No need to spend so long arguing about who has the right to snaffle up more than their fair share of bin space. If the hand luggage is limited to a reasonable amount then there is no issue with bin space up top. If people have paid for business seats and the bin space above those seats can handle more than the standard allowance then they can have more carry on allowance, but ONLY if the business class carry on is contained within the business seat bin spaces. On a recent couple of flights out of the US last month each person got onboard with at least 3-4 times the amount they should have. Bins were full in no time, before most passengers were even onboard. It was ridiculous, then we all sat for ages while the crew tried to sort out the mess so we could take off. What a farce.