I think the Dawi District totally makes sense for Cathay, I also think it would fit Kislev very well because the lore sometimes talks about their having limited ability to produce guns and trading for them. Alternately, a Reclaimed Dawi District at maybe Karak Vlag or Karak Azorn could be a cool Kislev version of the idea.
For the Central Ind Company, I think access for all human factions makes sense, maybe High Elves and Dwarfs too, if it's their sort of interface with local human trade. For the Governors Mansion, if it were possible & not too much trouble different versions for different human/order factions would be AWESOME in my opinion :), buffing different units for the different factions.
Slight side note, but using the Marienburg mod to play as House Fooger works soooo well thematically when you capture the Dawi district and it always makes my day.

Oh also I think maybe Vrindavanis' Animal Market could work for evil factions too? Or at least the ones that trade; I'm sure Dark Elves and Chaos Dwarfs would love it.

Here are a few ideas for Nippon. Bear in mind they are not based on any current lore, but do not contradict it. I just think they would be good for flavour.

Palace of the Divine Sun:
Palace of the God-Upon-the-Earth. - tier 3 and 5. Increase Control and Income. Expand garrison
Tower of Myriad Truths - tier 3 and 4, increase WoM, wizard recruit rank, but also spread a little Tzeentch corruption.

Miyukihama:
Kitanocho - tier 2, Increase Diplomatic relations with order factions and trade income bonus

Tsuranami:
Temple of the Sea god - tier 3 and 5. bonuses at sea, storm/ deep sea attr. reduce

Emishi village:
Kirishima Shrine - corruption reduction bonuses, buffed stats when fighting Undead

Dragon Fleet Port:
Imperial fleet Landing - unique tier 1, 3 and 5 ports. increase income, growth, trade
Samurai training ground - tier 4, increase recruit rank and garrison

Hidden Ninja Village
Shinobi school - tier 1, buffed ambush success and hero action success chance

Umikaze
Headquarters of The Interior Ministry - tier 4, greatly increase public order, decrease corruption
Sanyo Castle - tier 5, increase siege holdout, buff troops when defending

Mizushima
The Pale City - tier 4, adds frostbite damage to local troops, decreases enemy movement

Temple of the Orange Simca
The Defiant Temple - tier 3, Adds walls to settlement, increase in stats when fighting chaos