yes, definitely south chennai deserves a overnight train to bangalore, may be like MS/Tbm- SBC via CGL-CJ-AJJ (it needs loco reversal at cgl) or MS-sbc via cgl-vm-vri-sa-sbc(it also needs loco reversal at VRI) eventhough this route takes more time to cover bangalore but it will be useful for many enroute passengers like TBM,CGL, MLMR,VM,CJ, if operated in the above two routes. Many IT companies are easily accessible to Tambaram so it will be very useful .if operated it will be the first time connectivity to bangalore except VM(already pdy-ypr plying via VM).