Thats funny, how you say it, as every nuclear capable nation has proliferated nuclear technology, even sold it sometimes! And if no one leases/sells SSN/SSBN's explain how India is going to lease 2 Akula II from Russia, with the option to buy after the lease expires? Are you a Chinese government employee, that you're predicting they won't do something similar?
The just launched Indian nuclear sub, INS Arihant, is nothing more than a copy of the Russian SSN Project 971/Schuka-B [Akula I class]. Even the displacement is the same, however the Indian copy is slightly smaller with half as many vertical launch tubes & a reactor with half the power output of its Russian original. Only big difference is that it took Indian's some 30+ years to copy the sub and paint SSBN on top of SSN [figuratively speaking].
Oh btw, a SSBN is the 3rd leg [or strike option as you call it] in a nuclear triad, ground and air being the 1st & 2nd. Any of these three can be used for 1st strike but the SSBN's are considered more capable of surviving a 1st/pre-emptive enemy strike so as to provide a 2nd strike capability, its also the hardest to detect and neutralize.
Guess why India wont become any kind of power anytime soon? They will be bogged down in the South Asian sub-continent for a very long time to come, coz they keep picking fights with all their neighbors.
Superpower my foot. Just bring up the fact that India is just a poor 3rd world country with a per capita income of ~1000, [which cannot provide its poor and uneducated masses with the very basics, like food, clean water, living space or even bathrooms and] you'll see all these egotistic Indian's jumping up and down like bunch of primates! To these idiots India is the center of the universe, everything and anything must revolve around them!