you're talking about an openly declared war of total destruction
if russia continues it's economic, political, and social degradation, it will become weak enough that china can free siberia the way texas was carved from mexico: an uprising by locals, controlled by china covertly. buy off corrupt russian officials, provide "humanitarian aid", etc
then there is no war declared and no one for russia to nuke
russia can whine and bitch that china is supporting the whole thing, and china can just say it's a local uprising
if russia attacks china anyway, now muscular china has every right to openly attack dying russia
either way, you absorb the "independent state" later
sounds familiar?
yes, because this is how russia operates in abhakazia (georgian province), eastern ukraine, crimea: inflame, create, and encourage a puppet separatist movement
so what i'd like to see is: in 20-30 years china rushes in to "help" chinese minorities abused by russia
just for the irony
watch russia complain in blind hypocrisy
ukrainians and georgians are nodding their heads knowingly right now
already, chinese minorities in siberia are huge and a worry for moscow:
https://en.wikipedia.org/wiki/...
it won't be but 10-20 years before the chinese are running siberia by economic and social fiat, undeclared, informally, if not officially politically, with russia's weak economy and small population. the actual political control can come later, even much later
siberia breaks from moscow with chinese covert encouragement, just like russia in ukraine and georgia today, and china runs siberia as small weak puppet states