If the 092 and 094 SSBNs are stretched versions of their SSN counterparts, then the SSBNs are really reusing most of the existing SSN design, rather than the SSBN being designed around the payload.
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Personally, I'm not a huge fan of Chinese SSBNs because I think that even if they are quieter than ocean background noise levels, they are still too vulnerable.
China doesn't have suitable bastion areas like Russia.
Nor does China have unrestricted access to a vast "friendly" ocean for the SSBN to hide, unlike the USA, France or UK.
So I think China should concentrate on land-based ICBMs over SLBMs.
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Maybe they build another 4-6 SSBNs. But that will be far fewer than the number of SSNs we can expect.
So it is just easier to reuse the existing SSN design as much as possible.
NB. That assumes they don't have a new larger SSBN/SSGN design (20,000+ tonnes?) which has the numbers required to justify a new class.