Except, the IN viper doesn't exist. Only on paper. LM didn't even bother to do a full feasibility study on it when they realized:
1-India would not got for US equipment due to strict control laws
2-LM's ToT was limited to assembling rather than what India is trying to force Dassault into.
In any case, F-16 is not light weight. at 7.5tons of payload, it is well into medium weight.
Well, it is nice to lay plans on paper, but lets look at the reality:
India is inducting MMRCA to replace the Mig21s and using the LCA to fill up the numbers to more like 1 on 1. But by the end of the decade, Mig27s are due for retirement as well. Kargil showed that they are nothing but cold war relics, M2Ks beat them in any role hands down (which is what IAF realized and hence invested in their upgrades). So even if India manages to secure 126 MMRCA, and 50 more Sukhois as proposed along with the 150 LCA, it is still going to be only replace the Mig21 and Mig27 numbers. Squadron numbers remain the same. 42 squadrons is a lot of combat fleet, and that is not happening unless India proposes a MMRCA x3. Point being, in the next 10-15 years, you will be hovering around the 32-36 squadron mark because by 2025/2030 your earlier Sukhois, upgraded M2Ks and Jaguars would be nearing retiring as well.
About the two front war and Indian Fetish with China and Pakistan, i'd say that is an overblown paranoia and nothing more. Chinese and Pakistani nukes guarantee that Most of the MMRCA and Sukhois will never see the intended combat. So is it really worth it to spend copious amount on jets that probably will never be used?
Great for a logistical nightmare. While the world's leading air forces want to consolidate their fleets in single or dual kinds of multi-role, India wants to spread out everything.