They should be made independent countries. And then they should have economic cooperation and treaties between them. That will be much better than an indian union as it stands today. There are three leves of resource sharing:-
1) Water 2) Minerals 3) Food
For water sharing arrangement:- --------------------------------- South indians shares the river system which has origin in maharashtra. south indian rivers, so they could form a soft union of their own to.
Similarly punjab sares their rivers with pakistan. they should make a loose federation of upper north indian states to manage their affairs with pakistan.
Maharashtra and gujrat has some common culture so they can make a happy social setup in a separate soft union.
East indian states have brahmaputa river and culturally close to bengal they shoul make a separate political identity.
As far as MINERAL resource sharing is concerned, ------------------------------------------------ there should be a separate cross national (ie various future state countries) comission to manage that. That commission will belong to the future indian federation.
Food sharing arrangement can stay as it is with central authority for controlling prices nationally.