There was a thread earlier about the occupancy of BSB-RNC VB and apparently, it wasn't very great. Will Darbhanga - Ranchi VB be worth it?
The point is, two stations should first be regularly connected via something like a Mail/Express train that has larger carrying capacity and composing of GN/SL/3A/2A so that is serves the full spectrum of passengers. Won't introducing a regular night mail be better first than introducing a direct VB?