Do you celebrate your national day 4 days after it happens? How odd!
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Two new ideas:
Factory-like improvements: I´ve thought also of mining activities, smelters, saké brewers, and the like. You would need the necessary resource (iron, saké, gold, perhaps silver, etc.) in the urban radius, and of course you couldn´t make more than one of them in the same city. A smelter/foundry/sword forger would require an iron mine in the city.
Wako Pirates: I put them as a 2/1/3 unit in my homemade mod, and used the longship anim. They have enslave, sneak attack, and hidden nationality. Cost= 60 shields. Requires: Sueijijutsu, Jade. I say they could be used by anyone, and there could be a "pirate nest" SW (only for coastal cities, requires a harbor) that spawns a wako every, say, 7 turns.