"Lack of exclusivity pose higher risk to private passenger train concessions"
This could be a major hindrance. May be they could use airline model. Not more than 2 operators should use one route which has over 5 IR trains daily. For lesser connected routes, there should be only one operator. Further growth in demand should allow operators to add coaches and may be frequency, too. Who knows, like the skies rails would be ruled by private operators and not state.
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Also, platforms (at both, terminal and en route stations) should be reserved exclusively for the operators like no other trains before and after 2 hours of arrival/departure. They may be allowed to set up counters for their passengers at entrances to stations, too. This will facilitate them to clean, set up counters for sales, passenger assistance and advertising/promotions.