How do you think the discrepancies between China and Japan in aoe4

Such as feature of nation,building function and so on

Bushi/Mononobe (ranged cavalry that can switch to melee infantry) as special units, maybe some souhei (someone had suggested they could heal other units and the idea is pretty good, I think.) as well. ~ we have to satisfy the S-A-M-U-R-A-I fetish
I hope against all common sense we will get medieval Japan, even if everyone hates medieval Japan. ~ this would mean no Tanegashima rifles, no tower keeps, no stone castles, no invasion of Korea, all of the overdone tropes, basically
Get gold by killing enemy units, obviously not displaying the head-cutting part to stay PG13. ~in Japan, the only pay was for presenting heads of the people you’ve slain, the more important the person, the higher the pay.
No great stone walls, just like the Mongols. ~ Japanese did not build such thick city walls in the medieval era
Maybe some sort of fishing bonus. ~ fishing was very important for all of the people living on the coasts, which is to say almost everyone
Any destroyed building spawns low-tier spear units, like Poseidon in AoM. ~ strongly armed and militarised population

You could maybe include some sort of mercenary building, where you hire in small groups for the gold you acquired, but that depends on the balance.

The idea is to have a very strong infantry-focused civ. Their defense may not be great, but they don’t care for they want to keep up the offense. More offense means more gold which could thus be spent on hiring more wandering lords (or just build more strong units, if you want to be boring) to keep the pressure up.
We’d basically get a sort-of infantry version of the Mongols.