Would it be worth TOCs considering the idea of making a rule that if you don't have a ticket, staffed station or no, you must board at a specific door and buy one before taking a seat, say the rearmost door if the back cab is the logical guard place to sit?
No. It would not.
We live in the UK where there are ca. a million passenger journeys by rail every day. It is imperative that the Conditions and Regulations are as pragmatic (simple, comprehesible, enforceable, workable and, as far as possible, accessible) and intuitive to all who engage with them.
I'm astonished that anyone could seriously find grounds for further complexity while attempting to improve circumstances.
Any revisionism would be better focussed towards reducing the complexity of regulations towards greater simplicity, if a modal shift from road to rail is to be realised.