I think the Topic has been deviating, - The question is What Would an Islamic Indian Subcontinent Look Like?, not How Would an Islamic Indian Subcontinent Come To Be?
It would look divided. Many intermarriages between various rulers. I guess eating cows would be allowed... So... more cows in India to consume. More contact with the the Middle East with regards to trade as well as South East Asia. I'd see India as a place for Islamic Missionaries to be sent out to South East Asia and China as well as Australia if discovered. The most influental region in the Indian Ocean and more influenced by Persian culture and language. Odds are more Turkic tribes would be open to settle in Northern India as well as Pasthuns.