I like taliking about the game this way!
Self trade: About this civs “passive” abilities, I think self trade would be really interesting, specially when you consider the turks infamous need for gold in late games. I just don’t know this could be brought into the game with “reasonable” historical justification.
Gundpowder being avaiable in castle age is something I never got right. Turks have jannisaries in castle age, but don’t have handgunners. They get chemestry for free at Imp, which is great, but why not chemestry at castle, with some other change to compensate? Would they become to strong?
Archers in the barracks, I think it could on some other way, like Cavalry Archers being created at stables, mainly, perhaps, for the mongols, who seldom use foot archers. This would certainly make things for easier for turks, who get good CA and Light Cavs upgrade for free (I really think ppl would like some sort of buff to Turks/ I know I do).
*Herdables in mills I dont think it would make sense spend food to create food source (on game terms). But perhaps there would be a Civ that got better herds, i.e., letting a herd close to TC or Mill would let them increase food beyong its maximum by 50% over time, an then you could get more for out of them. Or even do that with hunt (except boars and alike), thus getting better food income in a further away timeline.
** Animals that dont rot** this should be basic stuff for the game, as in AOE4, but since it isnt, I think this could be a nice little touch to a civ.
If you`d like, please comment on this post I made, with also some crazy ideas. Bye!