I think that the current situation where the elderly and disabled get less compensation is discriminatory. Just because someone has paid a discounted fare doesn't mean that they have been any less inconvenienced than someone who has paid full fare.
I believe that the compensation should be based on the standard single fare for that journey, regardless of what type of ticket you actually held (single, return, season, rover, railcard discounted, whatever). That way the compensation would more truly reflect the journey length and relative inconvenience caused.