IMO the first question would India would need to decide the answer on, is what sort of system is going to be the primary means of air defence?
Once that question is answered, then various platforms required to create an IADS can be determined.
In my personal opinion, if the choice is between and airborne response, or a GBAD system, the airborne option is the better of the two. Air intercepts allow for a faster response over a large area, as well as things like visual confirmation and/or the ability to be re-rolled for CAS and strike missions as needed. GBAD system are limited in their mobility (for all practical purposes, they need an attacking aircraft to close with them to engage) and can encounter sensor limitations based upon surrounding terrain. This in turn could require a very large number of systems, as well as a very well setup IADS to provide coverage of all areas and at the same time, ensure that accidental engagement of blue forces does not occur.
-Cheers
In my opinion (from a non-def person) the air defense India should have is an IADS involving comprehensive and complete ground based radar (millitary radar and not civilian or dual usage) and anti aircraft SAM batteries and other ground to air assets, along with fast response long range supersonic interceptors (how about Mig-31 - is it of any use as an interceptor or only a recce platform) armed with BVR air to air missiles as well AEW assets as well as marine reconissance aircraft.
India is buying the P-81s and the Phalcon AWACS but i am not sure if the numbers are sufficent wrt the needs (8 and 3 respectively are the ordered nos of aircraft) apart from which India also operates IL-38s(5 nos being upgraded to IL-38 SD, am not sure its an AEW plus bomber platform or only a marine bomber)
Apart from which India had ordered the Pine Green Ground based weapons locating radar tht and mobile radar units should be aavailable in more nos apart from which there should be more satelities and UAV. also some hand launched UAVs apart from the big ones to be integrated into spec ops - infantory forces
I am not sure about anti-aircraft guns though - does it have any impact in todays scenario of precision guided bombs/ munitions being dropped from faster aircraft which fly higher than earlier crafts
To be specific i think my request is for a suggestion for the model for air defense fo India, we can talk strategy, kinds of radar and probably nos, kind of SAM units, UAV, AEW and marine recon assets and the required nos also interceptors