To be honest, I wish more TOCs had features of the train such as the wheelchair spaces, accessible toilet and First Class clustered together. You could even do what a few other countries’ railways have done, and provide a dedicated space nearby for any passengers who feel vulnerable travelling on their own (eg. some passengers travelling on their own late at night). This would mean that there would be one specific area of the train needing a higher staff presence, which would then be more easily defined and therefore patrolled by the crew, especially if it’s really busy.
(Obviously if you are doing guard dispatch then sometimes certain other positions would be needed due to platform length/curvature, but that could also neatly coincide with ad-hoc patrols of the rest of the train anyway.)
As for upgrading people to First - the vast majority of rail users (and even some rail staff) might be surprised just how often this is done for a variety of reasons. I’ve done it for many different scenarios, including providing a quieter space for distressed passengers; making First Class look busy in order to deter casual fare evasion through sections of journeys with frequent stops; aircon failure in Standard Class; heavy delays meaning people need power sockets to charge phones... you name it really. Having wheelchair users in there is probably a good thing all round for customer service, and the numbers travelling with more than one or two companions will be slim. The cost to the company should be minimal, if not in profit via good PR. There have been a few cases I’ve come across where it would be inappropriate, but very very few.
