At the risk of being cynical - does "flatten and simplify" also mean reduce on the off chance ? Because that's probably the opposite of what needs to happen at the moment given the yawning revenue gap there seems to be.
It means making things simple for a new world.
As somebody who spends thousands a year on the product, I would love it to be as simple as,
Long and Medium Distance
Advance - available until half the train is sold out. Probably the cheapest fares go up from where they are now except on the very least popular trains. If you want a massive bargain you will need to go at a time that allows the magic to happen. Max Advance fare is 70% of equivalent peak or off peak fare for that train. That will stop the ridiculous and out of order game playing that the clever people seem to love.
Advance change to T&Cs - if you miss your train, because there are a 1000 good reasons why you might, you pay the difference in fare between what you paid at the peak/off peak fare for that train.
Off-peak - I am not sure there should be saver and super saver or whatever it is now. Just off-peak. No returns, just singles.
Peak - will it ever be needed again on long distance? Who knows for now. Let’s say there will be some sort of peak though. No returns, just singles. No more than 150% of the off-peak fare.
Season tickets - you can have a 3, 4 , 5 or 7 day a week ticket. They are all pro rata so they give you a saving over singles/day returns.
Offers - rare, if ever. Why do we need offers, the clever people should be able to get the advance fares to do the job of filling the really unpopular seats. For the rest of the trains, reserve capacity for people paying proper fares.
Network Railcard - bin.
Metro services - no advance, no returns, just single off peak and peak fares. Season ticket as above.
Put all that through modelling scenario software tell it what revenue you want from the route and scenario test where you need to set the fixed fares. Let’s see where it comes out. Ideally, set the all the above in regulation so that it is, simple, no game playing.
Your advance fares are your variable to allow you to play around dynamically to hit revenue target on a day to day basis.
Open access - pays its way and has to accept above peak and off peak. Can do what it likes on advance except for the 70% cap which it just keep to.
Now I will prepare to hear a 1000 reasons why that simplicity is on mo way possible in the age of clever people and computers.