We can reach Vladivostok and Yuzhno-Sakhalinsk by container ship (the others are inland), but like I mentioned before you hit the second issue of potentially miffing and alienating Asian partners like Japan and South Korea, semi-aligned states like India, and opposing states like China.

And even Ukraine can't afford to alienate China given the level of control and ownership China has over Ukrainian industrial capacity and infra [0]

That's why we haven't seen incidents in the Far East to the same scale as those in Siberia.

Honestly, it's a tough nut to crack if the EU, UK, and the US don't provide boots on the ground but we obviously can't given our priorities in the Pacific.

[0] - https://geostrategy.org.ua/en/analysis/briefs/kitay-postup-h...