Good for the fun!
I can't see your 1st image in spoiler.
About your Euros:
1 & 3: the ice promotion protects Russian units from the winter effects in the 1812 scenario only (2 damage against 8 per turn - Morale promotion: 4 damage). I agree that otherwise the promotion is a bit useless but it's 1 mod with 3 scenarios... While I can play with this winter effect in a "special" scenario (1812), I don't want to extend it to 1805 scenario because 1) it's more complicated to code (south of map) 2) the AI has no clue of it anyway. The Ice promotion is given to the Russian units by the "Russian" trait, which also gives them CITY_GARRISON1. "Units have larger probability to win inside cultural borders vs fighting in Germany or Italy": I don't know how to code that efficiently.
2) Napoleon's traits. Aggressive is not so good, City Raiders promotion only (instead of Combat1 that I don't want to give, you have to earn it on the battlefield!). Charismatic is more important with the <iLevelExperienceModifier>-25. And he has Organized trait because he was. Aggressive, everything is relative. He was declared war much more than he did declare war. Ferdinand, Blücher, Gustav IV Adolf and Muhammad Ali have the Aggressive trait.
4) That's an idea but I sticked to the rule "if a Leader then not a Unit". Yes, war would stop if Napoleon had died on the battlefield - but that would not be fun. Forced peace and then what?
Oh... Suvorov died in 1800.
5) I don't know how to do that. Cannons are damaged too. Should I reduce Napoleon's navy even further?
6) Partisan unit. I don't really see what this unit could bring more than the other ones. Russia in 1812 scenario has 15 cities to produce musketmen (against 1 "French" city). Besides, pillaging roads and harrassing French troops was the role of the Cossacks. A partisan unit would best fit in Spanish guerrilla, but as discussed earlier, that is not yet on the tracks.
Thank you for this extended review and continue to have fun, with this Mod or with any other Mod!
PS/Edit: there is a "Hint" text about winter: "(Russian Scenario of 1812) Winter strikes from the first week of October to the last week of March. Unprepared units, who do not have the 'Ice' Promotion like Russian troops, will suffer more...". I agree that I should also have a "Concept" for that.