I think we're agreed here. With China being the largest emitter of current (as opposed to cumulative) emissions, a formula - which would indeed likely be quite complex - is needed here that can fairly take that into account along with the other points (like the accelerated timeframe required as compared to the rich countries).

The article makes a good point - which I think you allude to - about the definition of rich countries perhaps needing to be updated as part of this (for example, you include South Korea, who isn't on that list, though weirdly, Japan is, despite having a post WW-II date of the 1960s). Probably should be "advanced economies" instead of "rich countries" - so China would be rich via total GDP measures but perhaps not an advanced economy yet due to the low average per capital GDP or low average individual citizen's income, for example, while the US would be advanced and rich while (for example) North Korea wouldn't be either.