To what extent have Urdu and regional languages contributed to the development of Pakistan?
I think that Partition is a major component of this question. When the call to divide the Hindu Subcontinent was made, the line was fairly arbitrary in terms of demarcating what would be Pakistan and what would be India. There was little in ways of organic and authentic development as to what would become "Pakistan." The line drawn was one where majority of people in that section spoke and wrote Urdu. The poorly planned out and executed decision to divide the subcontinent was not made out of an understanding of the different languages or cultural traditions. A Muslim majority that was consolidated in the carved out of the two Muslim-majority wings in the eastern and northwestern regions of British India. Languages that were spoken there in those areas became representative of the new nation of Pakistan. One can say that languages as Urdu helped to give new identity to the new nation, but I am not sure that the verbal and linguistic construct of Urdu had much with the development of the Pakistani nation.