For me they could bypass Berlin and go straight to Brussels.
If the Russians take Berlin, you can be sure that all EU employees and woke politicians from the whole of Western Europe, will flee a few minutes later to NYC, Tel Aviv or San Francisco. Mostly San Francisco from the look of them. They've got private planes, they'd flee very quickly as soon as the first Russian tank enters, unopposed, Berlin.
Seriously, if NATO's stocks in Ukraine are really all burnt to the ground, Putin should say 'Poka and See you later' to the bothersome, brutish and tough Ukrainians, and quietly roll into soy Western Europe.
Ukrainians would laugh a lot and applaud, because Ukrainians secretly despise and hate the soy Westerners. Maybe Ukrainians would even roll themselves into Western Europe, just behind the Russian tanks, like hungry vultures, to loot and pillage Western cities.
This last year has proven that nobody, neither Russians nor NATO, will use nukes whatever the stakes. That is, if nuclear weapons exist.
So, we're back to conventional war. And if Ukraine has had its arms stocks destroyed, there's no reason to keep painstakingly fighting the obtuse, unmoving and poor Ukrainians, Putin might as well turn his attention to soy, soft and rich targets, the Western States.
If I were him, the day the last Patriot and arm storage facility is destroyed in Ukraine, I'd give the 'Nach Berlin' march order. Would be a lot easier and more profitable than Bakhmut.
Bakhmut was good to keep the thing on slow burner while NATO stocks were methodically bombed elsewhere, but if it's done already, what's the point and interest of Ukraine, when all the orders are given in the West. A West left with no Patriot and no shells and no manly soldier.
In the time it took for Russians to take one mile of territory in Bakhmut, they could roll through all of Western Europe while the local Yellow Vests would throw flowers at them.
In which Western country exactly would the oppressed natives not
welcome the Russians? Everyone in Western Europe hates the woke governments and inflation and islamist migrations, so everyone, Commies or Nationalists, would throw flowers at the Russians.
And the few Westerners who would not throw flowers at Russian soldiers, would certainly not fight them. To begin with, Westerners have no weapons, plus they are in general fearful and weak, and would in any case not risk their lives, whatever the situation.