Just my suggestion:
ER can think upon making this Vananchal express a 3 set of trains like
3 days a week via Sahibganj-Sainthia. (Reversal at Andal)
2 days a week via Banka-Jasidih-Asansol. (Reversals at...
more... Jasidih and Asansol)
2 days a week via Dumka-Rampurhat-Sainthia. (Reversal at Andal)
All these 3 trains can run at the same timings i.e. 7.05 pm Bhagalpur departure and 8.35 am Ranchi arrival. Thus end to end travelers won't be getting affected much.