It's an interesting idea. I'm all in favour of pillaging to curtail their ability to build any effective counter attack once we start on them. Here are my thoughts:
The only problem I can see with doing it during our remaining research period is that if we declare war and put our troops on Han territory we would probably have to flip to Monarchy pretty soon to handle war weariness, and that would slow down our research. Of course, if the Han decide to pre-empt then we should go for it as soon as possible.
Explorers are only 20 shields each, and they can move 5 tiles and pillage in one turn, so they have almost the same range as a bomber or kamikaze and a 100% success rate. Ideally they need infantry army cover to get within range of their pillage objective, but I think they represent pretty good value for their small shield cost. If we get back into a war with the Han they will revert to Communism pretty quickly, and their rebuild rate after pillaging will be slow. The AI never seems to stack more than a couple of workers on any single task.
Rubber is the most damaging resource to deny them, as it puts their land unit technology back to cavalry and rifles. They only have three rubber plantations, one on their western island, the other two dispersed inland on their mainland. We could hit them all in a couple of turns using explorers.
Oil denial will kill their sea and air capability. The Han have oil in five locations. Three are in the extreme southern tundra, all on the coast, and two in the small northern deserts. The southern ones are the only ones they have hooked up currently. One of the southern oil fields is under Shantung, so we would have to pillage all round Shantung or capture it to deprive them of all their oil.
Isolating Beijing is the quickest way to disrupt their lux trade as well as hitting their production and research capacity.
I'll try and put together a suggested Operation Stone Age map for discussion.