Maybe you're right, but that will not happen because of the secrecy. Only in the case of forming the full-fledged union.
To build a good nuclear sub is not just about the manufacturing capability, but also about many years of designing experience and knowledge.
Although inside of the nuclear sub is mostly made of pipelines and valves, which is a piece of cake for us. Also, our fourth generation nuclear reactor is also on par with the US, but to bring all these things into the design of the nuclear subs is a different matter as you need many years of accumulative designing experience and secret knowledge, there are so many tricks in the design of the nuclear sub.
If we can get brainstormed by Russia's secret knowledge about the design of the nuclear sub, it will quickly help us to catch up with the US in term of the nuclear sub capability with our current technology on the nuclear reactor and everything else.
As for the reward, we can help Russia to fully restore its surface fleet capability which was mostly lost during the split of USSR.
Just look at Ukraine, it looks like it won't get stable for a while, but fortunately that Ukraine's aircraft carrier and gas turbine technology is now under China's possession.
With these technologies under our possession, we didn't just copy it, but these things now get thriving under our own possession.
The gas turbine for example is now greatly improved from the GT25000 from 24MW to 43MW.
Many old Soviet technologies are now transforming into the new technologies, so we are gladly to offer in exchange with Russia. And I also think that Russia needs to take back these missing technologies since 1991 but in the more advanced form.