I agree some of your points and suggestions. One thing I regret for the game is Tower cannot justify its cost after castle age, and Hussar raiding is too powerful in late game.
Too dominant of Hussar in late game make Mangonel/Scorpion basically useless in open map late game, and civ lacking good hussar or halbs with bonus underwhelming in late game.
I also agree that imp Hussar can get slight nerfed. Maybe it can be done in indirect way of some units can be buffed against hussar. Give Champion (and 2HS) bonus damage against scout line to make them decisively win against them. They aren’t counter Hussar considering their gold cost in late game. Maybe it can be more drastic, but adding separate armor class for scout make them more bonus damage from spearman-line than before. (Similar to how elephant get more bonus damage from pike/halb than knight)
That also can be a solution, but make Tower in castle/Imperial age viable is first step to make some defensive structure other than castle also good choice to improve diversity. Garrison space of Guard Tower/Keep can be buffed to 10, Teutons can get 15 garrison space to make them valuable to place as defend villagers from raiding.
Also Arrowslits were nerfed so heavily, it can be buffed again to give Tower +4 attack regardless of the upgrade stage of Tower (+2/4/6 for each stage when African kingdom, and now +1/2/3, I think flat +4 damage can be middle ground). It can make civ access to guard tower (not keep) and arrowsilts can consider their Tower as viable option of defense in imp.