The facilities need to be not "taken down" but destroyed beyond any salvage or repair. Conventional attack to obliterate a large plant would need quite a lot.
If Japan started arming, and the S. Koreans cut off trade, then the Chinese might start to take notice of the spawn of Satan right at their border. Without China cutting them off, we can only set up defenses against them. America, OTOH, could tell Wally World to find somewhere else to get their crap from. There are many other crap making countries in the world to send our business to.
As a bonus, maybe China;s economy would slow, allowing us to buy some of their gas at a cheaper price. Right now, if we cut back and try to save gas money, we just allow them to buy the gas we should be using cheaper for themselves.
But then North Korea lets loose artillery on Seoul, killing hundreds of thousands. If you're going to start this war, it can't be a surgical strike; it has to be a war of liberation. However, China doesn't want a capitalist, united Korea on its borders, so they won't let the South take it all.
"The facilities need to be not "taken down" but destroyed beyond any salvage or repair."
I believe that in such a decision, simultaneous first strikes should be made on NK troop garrisons with daisy-cutter class armaments, at least on installations near the DMZ so as to preclude immediate conventional invasion of the South. Flattening Pyongyang should also be high on the list of priorities, while doing our best to avoid massive collateral damage to the masses of the general populace.