No use of running Dhanbad-Digha train sir and specially overnight train not required. Nobody end to end will travel if overnight train is given from Dhanbad to Digha via Dankuni, Mecheda route why such a Circular route for this. Not feasible sir. Dhanbad-Digha via ASN, Adra, kgp overnight train is also not feasible sir nobody will travel.
Yes u can try for Dhanbad-Digha intercity type train. In that case Asansol, Adra, Midnapur, Kharagpur passengers will travel, even Dhanbad to Kharagpur passengers will prefer. That is OK accepted, can be tried as special train. Good proposal.