The idea of ethnic / lingual identity driving nation state formation is a liberal idea (emerging out of the post Westphalian order)
The Roman Empire was cosmopolitan. So is the Empire of America today - holding together within it numerous ethnicities / languages over a continent sized land
So if you favor cosmopolitanism you should favor "Empire" models like USA, Akhand Bharat, British Empire of yore
Here nations tend to be small. Narrow. Xenophobic
Or worse a curious combo of ethnic and religious parochialism which is what Kashmiriyat boils down to
That should then favor large strong states. How about a continent sized India stretching from Peshawar to Andaman?
Very confusing
If you like diversity, heterogeneity, large states, free movement of ideas and people, please vote for "Empire"
Else please vote for ethno-centric conception of nationalism
(which is not as inclusive as you'd like)