So I went and did the thing with the invasion of China.
The size of their army was not as huge as I expected. I was told that China in this time period could mobilize millions upon millions of troops. Thankfully I only had to fight one 175.000 troops deathstack and a further 50.000 troops deathstack as reinforcements.
They disembarked as they always do, in Bengal, and proceeded to march north through the Tibetan plateau into the Steppes. Problematic, what with their non-attritionable nature, since I had to follow them into terrible terrain, but I handled it eventually.
As for the aftermath... There wasn't nearly as much fanfare as I had expected. I had really psyched myself up for the ultimate struggle of Ck II. Something close in scope to "Myklos Horthy and the Habsburg Prince" in HoI IV, but it wasn't nearly as terrifying.
Now I will get around to playing a bit with the boons I can ask for my daught... The Chinese Empress.
(Pics or it didn't happen)