In the international level, Vijay Shankar is useless and only good for a maximum of 1 over at best. In white ball cricket Thakur is bit n pieces and as far as Venkatesh is concerned KKR's ruined the bowler Venky and the newly designed Impact player rule killed all the chances of him bowling again.
One young kid named Nitish Reddy seems alright. He did well in Ranji with the red ball but too early to judge his white ball skill, his batting is good though.
Agreed on Vijay Shankar. Doesn't think that he will get an opportunity to represent India ever again. Nitish Reddy looks promising, and Venkatesh still has a chance. Thakur is volatile, but among all the names listed above, I guess he is the only one who can be compared with Hardik at the moment. But I seriously believe that Manishankar Murasingh can be a good replacement to Pandya. He has been in domestic cricket for so long, and I have seen him playing. But he represents Tripura, and the chances are there for near-zero.
Thakur already replaced Hardik in the red ball cricket (not for cricketing reasons but fitness) and Thakur is first choice seam allrounder in SENA. Both are clutch players but still, in T-20 it's tough for him to replace Hardik, maybe he can compete with him in the ODI but surely not in T-20.
Tbh never heard about Mainshankar, maybe because he's from Tripura and these guys hardly get any limelight.