... would it be good if the rice bowl belonged to the railway, and would it be even better if the national ticketing system handled the task in house with the cost wrapped into the initial advance booking payment.
Hmmm ... if you add flexibility to advance purchase "this train only" tickets, are you not encouraging people to move away from the more expensive flexible tickets, to the detriment of the overall rail industry income? There's an argument for selling "this train only" tickets to provide more economic travel to people who can go at unpopular times, but you start adding change options on to that and it gets confused.
I noted this in the publicity:
The power is in your hands. Swap the original departure time of your CrossCountry Advance train ticket, to one on the same day, that better suits your new plans. Swaps are open one day in advance and up to 15 minutes before departure, just ‘Swap & Go’. You can head home early, or stick around until closing time, it’s up to you. With Train Swap, you’re always in control of your journey.
It talks about it being CrossCountry, and perhaps they run trains up until closing time - but that still wouldn't work for me on a
GWR▸ advance / swapped ticket if I stuck around in London until closing time ... last train 21:30 which is much much better than it was, but I'm not in control ... can't get home like apparently I could with Cross Country