I get you loathe Russia in its current state Strongpoint, but neo-imperialist Japan is not what you want as a replacement.
Yep. Not to mention nobody on Sakhalin wants to be with Japan.
Do you really believe this? Should Japan offer locals full Japanese citizenship with all that comes with it, they'll jump in as quickly as they can. Especially after a few years of economic recession in Russia.
The same goes for Kaliningrad and Germany, Karelia and Finland, Kamchatka and USA (no I don't think that those countries have any interest... It is hypothetical)
I suspect that even Irkutsk won't mind joining China much.
Do you know how Japan treats their ethnic minorities? The Ainu say hi. They wouldn't offer jack shit. The truth is, most Russians are far less separatist than you think and would rather stay with Russia. I get it, you like Japan, but they wouldn't treat the Russians well. Besides as others have said it's a slippery slope for renewed Japanese expansionism which would be terrible.
Irkutsk joining China is completely out of left field, and honestly wouldn't be better than staying with Russia even purely politically. China is oppressive.
Anything from 1917 ver 2.0 to 1991 ver 2.0.
Neo-Stalinism and one huge North Korea is possible, but IMO, unlikely. Russia is huge and multiethnic
What happened in 1991 was that several regions with a strong historical national self identity broke away from the Soviet Union. It made sense, as a reversal of the post-WW2 state of things. Are there any regions left within the current Russian borders that have such a national identity, other than Russian?
With "1917 2.0", do you just mean the part where the tsar was brought down? I don't see a modern-day analogy of the ideological revolution that happened back then, am I missing something?
To answer your question, not really. Even places like Buryatia, Tuva, Tatarstan are very Russified, and it's mostly the Empire's and (to a lesser extent) the USSR's doing.