What we need is a proper peace negotiation system like the one in EU. Not just scripted events like the ones for Japan surrendering. They are a nice band-aid, but we need something better. You can't script events for every conceivable peace agreement.
In EU, you can declare war for a single province and as long as you can weather the storm, you can claim that province at the end of the war. There is even the ticking war score system that means you can win the war without firing a shot or taking any other province, you just need to hold hold onto the province you want, and eventually the enemy will cave and let you keep it.
With China in HOI4, I don't have such options, so while I could walk in and take the whole lot, I would be at war with Britain for all time, or have to travel around the world to invade England.