Your proposal is good to shift Puri Garib rath exp from Howrah station to Sealdah station....... but platform availability at Sealdah is problem. Although 1 no. New Platform at Sealdah ( Pf# 9D) is built but still evening departure is doubtful considering the present rush at Sealdah.
Shalimar stn shifting will be done by SER soon but i feel Shalimar stn still has poor connectivity....better connectivity be it Road , Bus, OLA, uber, Ferry service, EMU trains more to be runned. All these connectivity still needs to be improved more at Shalimar stn.