I think Gitanjali had sacrificed some rakes to give it some newbie trains of SER. (As to run Gitanjali independent on it's, it will require some 4 rakes of 24 coaches each)
Instead Jagannath Express can do RSA with Kurla Shalimar Express, in my opinion (that will also save the trouble of attaching & detaching pantry car, as Jagannath Express has no pantry car)...