Rather than rewriting history now, I think China would do far better to blatantly object to any rules defining sea territories based on what small islands the nations who were eager to colonize managed to seize, back when; and instead argue that taking the population densities in the area is reasonable when divying up the sea. That's their real point, and it's a pretty good one.
The trouble with inventing claims and shoving military forces into places you'd like to have now, is that there's no end to it. It's a promise of eternal war. Eternal irredentism and revanchism. Bound to make 'em unpopular. China could make a legitimate argument, in my view, but even now they aren't bothering to do that. Pity.
I'd rather China invited other nations to discuss creating a law of the sea that's more reasonable than "small island theory" that comes down to us from colonial times.