SRC-ANVT express not needed, rather TATA-ANVT Superfast Express should be run, another RNC-ANVT can be run via BSB,LKO,MB.
New trains from Kolkata to Delhi should run via the dedicated HWH-NDLS GC line only. At this instant Kolkata doesn't have any other good SF for NDLS other than Poorva.
SHM-LTT via BLS would be a big circuitous route as you will likely have to take either the route of Konark, that is the amalgamation of the HWH-MAS and the MAS-CSMT route, or the BBS-TATA route at CKP, or through a reversal at BBS...
more... and going via SBPY. All of them are hugely divergent routes.