Grand ideas strike again! This scheme was already introduced (tie up with SBI bank) way back in 2004 when IRCTC started online ticketing and discontinued later as it flopped.
In order to be frequent flyer, first step is to eliminate restriction of 6 ticket booking per month on irctc! Probably no country in this world has such a restriction on booking simple domestic train tickets. First make money, then offer discounts and other ludicrous offers! Those days are left in ancient history when big airlines of the world used to award big rewards to their dedicated customers!