What really worries me is what happens to supply line adjustments at such enormous distances - if you move a division in the Far East two provinces from its usual location, how many weeks will it take for the supply line to actually adjust? How do you invade Manchukuo with a large armored force if those tanks have to run on their own supplies all the time?
How indeed? I imagine that something like offensive supply would keep the tanks supplied as long as the offensive was quick, but Manchuria would be a case where supply lines should take a while to set up. During the Chinese civil war, the Nationalists confined themselves to the cities and railroads because, even though the terrain was flat, they couldn't supply troop concentrations in anywhere but the cities.
To take your example, A soviet armored strike should be viable, but they better end the offensive parked in Mukden or Harbin, where they can be supplied by rail. I also imagine that there would be an existing Russian supply depot in Vladivostok to supply those divisions directly. This way, the initial push comes from a mix of the on board supplies and those drawn from Vladivostok. Vladivostok is supplied from Moscow at a substantial penalty, but that won't come into play until the Vladivostok dump runs out. So let's say that the Vladivostok depot is being sent 30 supplies from Moscow receiving 20 supplies everyday a 33% supply distance penalty. At peacetime the supply consumption of in theater units is 15. The depot fills up until it's holding 1,000 surplus supplies.
The offensive begins!!! Multiple divisions bridge the Amur River while Soviet tanks pour out of Mongolia. Supply consumption jumps to 50 every day, but they have a 30% penalty from the low infrastructure, so they are drawing around 70 supplies from the Vladivostok depot. Once that runs out (roughly two weeks), they start drawing supplies directly from Moscow and the supply route is drawn across the entire distance, giving a 63% penalty to the advancing divisions. Troops would need to rest for a while to allow the Vladivostok depot to fill up again.
You might ask what's the difference then? But mathematically there is one.
For the first two weeks, every 100 supplies sent from your capital would be reduced by 33 on its way to Vladivostok and then reduced a further 20 supplies on it's way to the troops. Out of the original 100 you have lost 53 supplies in transit. The infrastructure penalty on the divisions fighting, however, is still only 30% because they are drawing supply directly from Vladivostok.
Once the divisions use up that depot, they are losing 63 of every 100 supplies and the troops are fighting at a 63% penalty.
The numbers are made up but I imagine that a supply depot system will make it so that most of the time troops won't be tracing their supply directly to the capital for the purposes of the supply penalty. Ultimately all supplies come from there and losing the route cuts you off but there will be a time lag.