No, it will not make any impact. Gaya-BSB got train on same timing as Doon Exp!! BSB-RGD/Gaya is daily connected via Shramjeevi/Budhpurnima!! BSB-BGP is connected by Upper India. BSB-KYQ is well connected.
You cant expect full train to run for just BSB-NWD!! This train's full occupancy in Gaya-BGP shows that stretch is used like ICE!! And if they are Ticketless (Not Pass Holders & Passenger Ticket Holders) then scrap this train in Gaya-BGP!!