S&T there will always be the case where a 'passenger of reduced mobility' is boarded last otherwise there will be no chance of any aircraft departing on time purely due to the co-ordination of getting a wheelchair passenger through the terminal and to the gate at the relevant time.
Lifting passengers onto the aircraft may not be aesthetically pleasing to watch but, again, it may be a necessity due to the unavailability of an ambulift vehicle or in fact the incompatibility of an aircraft with a particular type of aircraft.
IMHO, tact and respect go a long way in these situations whereas the blind application of directives will surely cause an unworkable logjam. As for some people taking the p!&& out of the rules, it is amazing how some people jauntily climb the aircraft steps returning from holiday only to suddenly require a wheelchair just before top of descent!
