There is a way to trade the illegal pairs, legally aswell.....
if you want to go long on say EURGBP then just buy EURINR and short GBPINR, this results in the pair EURGBP. Formula is (+A/-INR)+(-B/+INR) = +A/-B, INR is cancelled out,sp u are neutral on INR and have exposure on the other two currencies. You can do this with all allowed pair combinations.