There may be a limit of what you can do with old embedded system software almost certainly written in assembly language.
As another example, people might recall that on Southern you get train-side displays saying something like:
This is coach number 1
<scrolls>London Victoria.....calling at Nowhere, Anywhere, Somewhere, Clapham Junction and London Victoria
...which while useful is really not the optimal layout for such screens. However, I suspect the screens are relatively hard coded (i.e. on a physical EPROM) to do a fixed first line plus a scrolly message sent in via RS232 or similar, as the original layout was something like the following (as still used on other Electrostar and 172 TOCs who don't do as much portion working):
London Victoria
<scrolls>calling at Nowhere, Anywhere, Somewhere, Clapham Junction and London Victoria
So what they did was a pragmatic choice that allowed the information required to be provided. But not the ideal which would be something like:
Coach 1 - London Victoria
<scrolls>calling at Nowhere, Anywhere, Somewhere, Clapham Junction and London Victoria
or somesuch.
Therefore to me any solution (certainly in this franchise) is going to be more of a procedural one, such as announcements and stickers that reservations apply regardless of display and to go to the unreserved coaches without (which need to be unreserved fully at all times, no overspill into F etc). That way they can be downloaded en route, and then once verified an announcement could be made saying people standing should go and try again.
Or somesuch, e.g. the other option of trying a couple of times then switching it off and declaring a free for all. Again, it barely matters what it is as long as there is one and it's clear - presently it is not, and it causes conflict and stress unnecessarily. I don't think it works leaving it to staff discretion, I think a clear policy is needed to be followed at all times and to be well publicised.