If it's gonna be used for LTT/Pune Service the train should start from Kanpur either via Allahabad or via Jhansi. It's about time that Kanpur gets a proper dedicated connection to Mumbai/Pune.
Although even a service to Mysuru (via Bengaluru) or Coimbatore (via Chennai) would attract more than decent crowd from Allahabad alone.
Filling up a dynamic fare train on Mumbai route is not a big deal for Allahabad when we consider the patronage of Duronto and patronage from Jabalpur and Satna enroute. But I think if it's going to start from Allahabad...
more... it should go further to Pune (via Panvel) like Santragachi Humsafar as Allahabad doesn't have a dedicated connection to Pune yet.