The reasons for Mumbai's population growth has a lot to do with Migration. Early on it was nothing more than a backwater province till the British built it up and converted it into a commercial centre.
In modern times it owes its growth more to internal migration from across Maharashtra and Gujarat than anything else. Perhaps there could be a simulator of such a sort where people move from one city to another depending on wealth and health factors. Otherwise, Maharashtra and the region around Mumbai is not rich in food resources. I feel we should avoid trying to make an unhistorically early growth for cities around western India.
This means that all the food produced is on a network and then the total food is given to the cities with a certain mechanism. A similar mechanism exists in colonization, where everything is traded between cities including food and hammers. I would like to see it. Maybe it could be a variant of corporations. For example, let the cereal corp to reduce all wheet resources by one food and deliver them in your cities.