Another equally (perhaps more) important reason for a big or growing private airline in India to have a good number of expats (albeit higher salary/perks in comparison to his/her national counterpart) would simply be to maintain absolute power and prevent any kind of a united action by the national pilots.
Like the strike or mass sick leave done by Jet Airways pilots last year.
The bean counters would want to avoid another such situation and Im sure they have short or long term strategies in place already for that.