There are millions of Maharastrians in MP, UP and Chhattisgarh. Go and visit Indore, Gwaliar, Bhopal, Jabalpur, Raipur, Durg/Bhilai, Kanpur and Delhi. Why? Because India is one country. If people want to stop migration of people and force them to learn non-mother tongue laguages (not by choice but by force) then we should go ahead and spilt India into multiple countries? Why create this drama of a NATION when we don't even follow the basic defination of a nation, which is no one can coerce and bully you? Once India breaks into these 600 countries again (as was before 1947), I very much doubt that each of these nation states can even stand up to Afghanistan and Bangladesh, much less Pakistan.
