The fact that the top poster on this forum is in fact the Fares Advisor with over 23000 posts speaks volumes!!!
I could spend a week on this topic but lets start with something simple.
There are currently 5 types of National Railcard which cater for a cross section of the population........the only ones that are not catered for are single travellers between the ages of 25 and 65.
I would suggest we get rid of all current railcards, and replace them with 1 single one which entitles the traveller to 33% off fares after 9.30pm....the cost of the card to be the same at £30.
As you point out , off peak should be the same everywhere - ie after 9.30am
I'm assuming you mean both of those to be 9.30am?
That'll disadvantage the many Northern fares which currently have an off-peak time of after 0430.
It'll make the first train you can get from Edinburgh to London on an off-peak ticket the 0930 instead of the 0548.
This'll mean lots of people will start splitting their tickets at the first station they pass after 0930 - making their ticketing more complicated.