You can perform all of the mental gymnastics you want but it's far simpler to just buy oil at the market price via maritime route. When these other countries implode economically as you magically say they do oil demand will also drop. Meaning all these said investments in oil and gas will just become useless once demand destruction happens.You're still struggling to understand the real world: money is fictional, the cost of energy isn't the energy itself but everything downstream that require energy to function. Yes if Europeans has to lose access to Chinese goods for China to import energy, Europeans will lose Chinese goods, because money from export to Europe are worthless without ability to buy real things with that money.
But it's also an entirely moot point because even if you ignore China and central Asian section of the route are double track, rail is hardly the only nor even the main trade route between China and Europe, something I will be generous and assume you simply forgot and not ignorant of, diverting export rail cargo back to ship literally cost China nothing as it will be entirely up to Europe to pay the cost difference.
Having said that you're making good progress in understand why capacity is all that matters, but it's not about the track or gauge or terrain (please review high school physics again), it's limited at loading and unloading, which will require infrastructure investment to expand. But as for who's going to pay for those, it's whoever without that infrastructure, i.e. countries currently starved of fuel, and countries who need to import Chinese goods, which is now everyone when China's the only country who has fuel to power their industry.
Do you get it? In the real world only real things matter, it doesn't matter what that money cost is, if you have access to energy and others don't, you're going to make a profit one way or another, be it through direct resale of oil, or through monopoly of all industrial outputs that require energy.
Try and keep up with basic math.
As someone whose actually visited TMX terminals yes I perfectly well understand the viability of crude by rail, something @iewgnem seems to not.Canadian oil transport by rail basically died ever since TMX came on-line. It was a desperate move when Canada had no choice. China is far from desperate.