God knows when that line will come up (in how many years), plus at best it'll be a single line which'll probably be good enough to support freight trains and a handful no. of local/MEMU trains only may be (again depends on ER's mood). But without any route change or muchtiming change, this could be a perfect daily connection from Bengal to Kerala (with touchbase at Kolkata/HWH), maintaining MPS at 110-130 kmph (not possible via some random Sripat Srikhanda).
Train departs BLGT at 20:40 as usual, passes MLDT at 23:00, AZ...
more... at 01:25, Bandel to HWH 40 km section can be speeded up, such that it reaches HWH by 05.30 and departs by 05:50 (after 05:45 Duronto), and exactly 39 hours later (standard avg time between HWH and ERS via PER), it reaches ERS at around 21:00 - 21:15 hours the next day (running ahead of 22670 timings)!
Likewise it can depart 16:15 from ERS (shortly following 12625 Kerala SF and run ahead of 22640), reach HWH the third day at 07:30 (after the entire brigade of weekly/biweekly Odisha trains and Hatia Kriyayoga), and depart as usual towards BLGT at 07:50... If this train is controlled by NFR, then comfortable 27 hours PM time at BLGT! (but will require 6 rakes; lesser if controlled by SR with RSA, but only couple of hours to turn around in BLGT)...
If ERS cannot handle a new train so many additional rakes, better to hand it over to KCVL. I mean, options are wide open!