Nescio

The bixie (píxiū) as a mythological animal (a winged lion-griffin-chimaera), yes, that certainly existed in Han China. The Parthians are known to have gifted lions to the Han court, which probably contributed to their popularity. Two more examples of Han statuettes (both under 10 cm), one jade, one bronze: https://www.christies.com/en/lot/lot-6268189 https://www.metmuseum.org/art/collection/search/823655 Bixies as an architectural element is a quite different story, though. Here's how they're used in the 0 A.D. Han mod: One detail that particularly struck me is that stone orb. It's important to realize the dragon, bixie, qilin, and guardian lion are all distinct animals. In more recent times, Chinese guardian lions (shī) were erected in pairs in front of government buildings, the left one the female (yīn) with a cub under her left pawn, the right one the male (yáng) with a cloth ball under its right pawn. I don't know of any bixies with a ball. Nor of large stone animals in front of Han-dynasty government buildings. If you do, please let me know. To summarize, while it's a nice detail, it got the details wrong. I'm not advocating simply removing the stone bixies from the structure: the stone platform and the stone stairs are problematic too. I don't see an easy fix here.

Clay? No, rammed earth is a fundamentally different technique than mud brick or adobe. I vaguely recall discussing that in the other thread. The existing structures are not really representative for the Tang dynasty (AD 618–907) either, however, historical accuracy is less important for mods, so feel free to (re)use them in Millennium A.D. Here's a suggestion for an appropiate wonder, the (fired-brick) Giant Wild Goose Pagoda in Xi'an:

If the Athenian champion is supposed to be the Iphicratean type, then it shouldn't be called ἐπίλεκτος. The important difference is the peltē is rimless. As for its size, have a look at the east side of the Tomb of Payava from Lycia, c. 360 BC (nowadays in the British Museum):

There are probably more examples of elite units looking more impressive than champions in 0 A.D. That's not exactly true: ἐπίλεκτος (plural -οι) simply means ‘chosen’, they were picked troops, selected by the commander to serve as his bodyguard, fight on the right-hand end of the phalanx (the most honourable position), or for some other task. They didn't have some superior equipment that set them apart, nor were they a standing corps. The same is true for the Latin extraordinarii. In Iphicrates' times Greek states increasingly relied on mercenaries, who could be drilled, disciplined, or dismissed, unlike citizens, who were nominally the equals of the leaders and could sue their commanders after the campaign was finished. Moreover, there was more emphasis on mobility, which is why Iphicrates equipped his troops with boots instead of greaves, dropped the bronze muscle cuirass, and replaced the heavy ἀσπίς with the lighter πέλτη (hence the name ‘peltasts’, for what were essentially proto-pikemen).

Wood was the primary building material in ancient China and rammed earth was used for platforms and defensive walls. However, the mod's existing tower has stone architecture (as do some other structures), which is wrong (as is that Qing dragon flag):

Having map-specific mercenary camps is something I'd like to see too, and it has been proposed multiple times in the past (e.g. here or here). The suggestion to make embassies prerequisites instead of unit-training structures is interesting too. Anyway, proposals aren't either-or. As with everything, discussions on the forum are nice and all, but what's needed is someone to actually do the work. If nobody creates a patch, nothing would happen. Ranged troops don't get higher resistance or attack damage. Moreover, there is already a technology that makes mercenaries start at advanced rank (added in A22). And keep in mind higher ranks are worse at gathering. Fundamentally the idea is to make mercenaries somewhat in between citizens and champions.

Han model of a two-storey tower: Han model of a three-storey tower: Han model of a four-storey tower:

Have a look at this thread. Stone walls, paper lanterns, and Qing dragon flags are some of the things the Han shouldn't have: 0 A.D. is not a Disney film. Perhaps you could start with designing a new fortress or new towers?

That's for companies, I suppose (and there is an exemption for free and open-source projects such as 0 A.D.). Individuals can sign up and join projects without having to pay anything: https://www.transifex.com/signup/?join_project=0ad

https://www.transifex.com/wildfire-games/0ad/

One thing people love is 0 A.D.'s attention to detail and historical accuracy. Including the Han into A24 was discussed some time ago. It didn't happen. To the best of my knowledge, none of the issues of the Han mod has been solved since. I fail to see why it's suddenly good enough to be included right now. Again, I'd love to see the Han included in game, if possible in A25, and no, not everything has to be perfect. Nevertheless, the most glaring flaws should be addressed first.

There is a proposal to make mercenaries start at advanced rank: https://code.wildfiregames.com/D3699

Yes, I fully agree the current situation is far from perfect. Nevertheless, I'm unconvinced limiting player freedom (or breaking the AI) is the way to go.

That's actually a depiction of Rome in the 16th C AD, when the city was still much smaller than in Augustan times and people were farming inside the old Roman city walls.

That's actually doable to get committed, A24 had several such changes. I meant art improvements, some examples I've requested more than once on these forums in the past. Britons and Gauls shouldn't have a donkey trader, Athenians and Spartans should. The SQPR ought to be removed from Roman wall textures. The Roman civic centre needs to be replaced. Macedonian dock. Wall towers. I'm fully aware the art team is very small and can't do everything at once. However, when there are already so many things that still need to be improved, I don't think it's wise to include a lot more assets that really need to be replaced.