I mean, part of the issue with the whole Cathay/Old World strengths/importance and such is that, well, GW just never developed the Far East further than they did. Which is, pretty much, just a few throwaway bits compared to the utter wealth of the Empire/Brettonia/Ulthuan/Etc. stuff. Books, codexes, warscrolls, and so on.
Like, parts of Cathay irritate me, in that GW clearly just mashed 'Asian' together into one country. Bannermen of Cathay are just Samurai, honestly, with the label sanded off and painted over in block letters. Ki-Rin vs. Qi-Lin, is another one, as I noted before. Languages means things, and are different. They could have said the people of Nippon call them Ki-Rin, while in Cathay they are known as 'Qi-Lin', but they didn't. The crow-men are clearly references to Tengu...which are a Japanese thing. As are Shugengan! Pretty obviously derived from the Japanese religion of Shugendō. They also have turtle-ships, which are Korean in origin.
So...if we
ever deal with Cathay in closer detail, in any of my quests, ever, there's going to be some pretty significant changes. Like...Tengun, being actual living crow-men who live in Nippon, and the crow-men being but imitations of them. Or maybe Tengun are really magical statue things, but they're a Nippon invention, because fuck Cathay's already got stone dogs/Jade Lions/terracotta. Straight up stripping Cathay of calling their wizards Shugengan, I'll find something else from Chinese stuff, because...like, come on. That sort of thing, yeah?
But also, back to the original point, the Great Bastion is hundreds of miles long, it has a garrison that is tens of thousands strong all across its length. The armies of Cathay are supposed to be innumerable, they have the Jade Lion living statues, the living statues of Crow-Men, terracotta automaton soldiers, they have a bunch of dragons roosting, the monkey folk, the hill peoples, the cannons, the enchanted fireworks, their own magical traditions, etc. etc.
And GW gave them all that because, I suspect, they never intended to have to go into depth with it. So why not make it sound as fantastical and amazing as possible, because all of their stuff is going to purely focus on the Old World, and the New World, and only have passing references to the Far East. Leaving it to GMs of WHRP to probably homebrew it for their own tabletop campaigns and such. Fun little art pieces and minis, hurray! But nothing serious or involved.
Then in the End Times, they go up in a puff of smoke. Sure, the Dragon Emperor and his forces beat back the forces of the skaven entirely, and stalemate the world-ended invasion of Chaos. Then Grimgor comes over, wins immediately, and then turns right back around to go back to the
real important part of Mallus...the Old World.
Honestly. It's like they didn't think that several years after creating their universe that some idiot with a keyboard wanted to do a quest which would involve a whole lot of that planet that they invented.