The amount of rail cards on the market is reflective of the complexities of the ticketing system itself. It is mad when you see all the options.
I would just simplify it and offer something along the lines of:
- A concessionary railcard (so includes seniors, veterans, disabled, 18-25, etc) all under one umbrella, with the same discount of 33%. Most seem to be the same price and discount anyway.
- A regular user railcard, similar to get German system would be great (25% for £200 a year, 50% for £400 a year, with big discounts available to annual season ticket holders). You could also offer a special price on two of these for people who travel together to replace the Two Together (which is a great initiative).