Going back to the boarding / check in issue, and staff workload in general the key issue I observe is the demand for 'everything to happen' in a very short time window before departure (a hotel, for example, would not expect all the guests to arrive in a very short time window). Then also there are all the queries from passengers just boarded who are unfamiliar with cabins etc, plus a daft demand on the brek menu form asking you to give it in something like within 30 mins of departure creating more rush etc etc
This problem extends to the staff in the bar car who are too busy coping with the number of people requesting service in the window of time immediately prior and after departure, there are not enough staff to deliver on the expectation of the pre journey publicity (eg ref food service), as CS are much hyping their food offer which creates demand at this core time.
Logic would suggest the provision of some staff that just work the train for this 'early journey' leg, - eg travel north as far as say the Crewe or Preston stop on the highlander, as clearly later on when more people are sleeping, there is less need for staff doing those duties. Or even just platform check in staff that allowed train staff to focus on customer service on board only at this vital time window.
Of course the fragmented nature of the railway, plus the shift patterns that this would create, would, I assume make this very hard to do. But of course in much of the zero hours culture of the hospitality industry, this is probably what would happen.