Instead of asking for retired Kilos, if a mechanism is worked out for newer Kilos meant for Pacific Fleet to be transferred on a 10 year lease to India. That solution is actually good.
Might be a bit more costly, but will be quicker and safer.
New subs can't enter service in 3-4 years. It's the same story. All we can do today is stopgaps, either second-hand Kilos or upgrade and lease some old Jap or Korean subs. Soryu is an option, and ToT is not expected.
Our induction program has been scheduled in such a way that we will get 18 new subs between 2030 and 2040. So, today it's about buying time while waiting for those 18 subs. And buying time would mean inductions within 3-4 years of contract signature for active duty until the replacement period between 2035-40. We basically need 6 old subs to survive between 2035 and 2040, to promptly be replaced by the P-76, which is where the 3+3 Kilos fit in.
Alternatively, forget the stopgap, we can just upgrade the 3 Kilos we have. It will mean a shortage of 3 subs after 2035, but 21 is still a good number. It can be made up with an additional SSN lease.