As mentioned in other PN thread, the following is the most practical choice...
PN ought to concentrate on Chinese SSKs that are in development phase based on the 039C (4k tonnes) class design with VLS (like South Korean SSKs).
There are unsubstantiated rumours that the Chinese are developing mini reactor of this type.
It would be ideal if PN went that approach & 8 such AIP-SSKs (N) with VLS would extensively enhance PN capabilities & refrain from having to make significant investments in SSNs to counter IN's SSN threat.
Further, Hangor & Augusta fleet will complement this type while PN is also in talks with Italian shipbuilder Fincantieri for their S800/1000 Shallow water SSK based on U212/4 design to replace midget subs.