No, I don't think that singlevcitizenship is useful now-a-days because people now are representing from their own states and not from the name of the country. The proposed Indian constitution is a dual polity with a single citizenship. There is only one citizenship for the whole of jndia . it is Indian citizenship. Every Indian has the same and equal rights of citizenship, no matter in what state he resides!
Yes. I think it is useful in the present scenerio because as the India is vast country and many people who were below poverty line cannot effort money while migrating from one place to another. If we see America it is a duel citizenship central, state. So they need passports to travel from one state to other. As some times unity doesnt exist. But here in India unity exists and all states equally develops as India opted single citizenship. Gives equal rights to all people amd equal rights for questioning the government.