Someone the other week was talking about something similar to DB's monthly ticket (all non-fast trains for £50 a month).
And that got me thinking just how awesome it would be. TOCs get guaranteed income, people get easy travel.
£600 a year, to just hope on a train whenever you want (so long as it isn't fast).
Hell, give it to the over 60s/under 30s/jobseekers free too.