If the US allowed that, then what would stop Russia from providing Iran or North Korea with nuclear weapons, or ICBMs? You do realise there are strategic consequences to escalating things, Russia does have hands they haven't yet played. Ukraine gain very little from attacking anything actually inside Russia apart from some social media post saying they blew up something that wasn't even really involved in the war with Ukraine. Their main concern should be the 500,000 Russians sat behind defensive lines in what used to be Eastern Ukraine, that's what their weapons should be used for.
Not aure (given the reputation of tussia arms) they want any russia arma, more likely they will look to develop the tech themselves based on shared knowledge.
Strategic consequence - you mean russia threatening outsde of fhe Ukrainian war? Possibly UK?
All countries have hands they’ve not played yet. Sorry but the agressive rhetoric seems to be a scare tactic.
The engagement of other countries directly undoes the political war and also opens up a second front which has a completely different landscpe - russia would loose its small remaining navy, needing to build more and find yet more resources lost thay require funding..
If you’re meaning using Chinese naval hardware using African ports as bases? I think that boat has sailed - china will not want the politixal fallout nor expose the literal cracks in their hardware (a number if built carriers have cracks in their decks due to bad manufacturing that made the unusable).
Russia’s targets are the easy soft undersea or offshore assests - attacks would end up the loss of those vessels so instead a land based war of attrition enables BRICS support without bringing into war. If china get too involved it’s likely to see trade reduction resulting in china going deeper into the economic red. Internal political impact on Xi will limit.
10-30 years and Putin will have died. The legacy will be a new generation of beainwashed russians ans politics. The duma cartel leadership will also have changed, and I suspect at that point they will have the financial fallout of Putin’s actions.
War is expensive and the spoils in ROI take years if jot lifetimes to recoup.
So in short I see russia only wanting to engage small conflicts and switching to economic and political war to separate nations, isolate in a form of silk road initiative.
In your post you simply remain vague and ambiguous - hinting threats. It is more likely that putin relies on sympathy to enable coercion of the political landscape and in the UK Brexit to divide a response.