If China is united (and expanded), with good techs , population x3-4 as whole UK+colonies where is challenge for player when he play as China, or how to beat them if you play as other country?
In previous versions I remember , first or second step was to take some provinces from China early if you want become GP 1, and avoid +4000 brigades against you
You live in Lala land... "United" - never happens to AI; "good tech" - good luck with less than 3% literacy; "population.." - you mean the chore of manually building factories everywhere with no capitalists whatsoever and massive emigration whatever the players do; "challenge" - always there, just not as rewarding/fun as Europeans; "as other country" - any historical GP can do it easily even in AI's hand, players always win no matter the country.
If you had to take provinces from China to become GP No.1, you simply didn't play enough Vic2 (or you just suck). Ask for tips on the forum about the proper way to play Vic2 instead of whining about a imaginary China that never existed.