I was thinking about it and want to hear ur opinion.I havent tought deeply.I am going to cite my ideas here superficially.Maybe I think about the details in the future and write again in a new heading.I want to hear your opinions and would love to discuss.
Spain:
Colonization:Building a new tc and barracks far from your first tc is cheaper
Spanish gold:You gain gold from destroying town centers,wonders and trade centers.
Tercio Pikemen:Better Pikemen with longer spears
Tercio Musketeers:Lower healt than other musks. but more range
Conquistadores:Cavalry that gets stronger when he is far from town centers.It gets stronger the more they are far from town centers enemy centers are counted too.They could be like in the Medieval 2 total war
Missioneries:Healer units mounted on donkeys.Heals units and makes them faster.They can be like in Aoe 3
Denmark
Raiding:Killing villagers,caravans and destroying eco buildings with infantry gives gold more if you do it with vikings you gain more
Vikings:Replaces men at arms have more attack and throw axe or javelin before encountering in melee but has less armor.This skill has a cooldown also the range is too short so you cant hunt any ranged unit from far.
Jarls:Works like japanese retainers.Rises the attack and speed of the units nearby for a short time they can be trained from castle.
Housecarls:They can be called from town centers for a short time to defend your town centers.Housecarls were the bodyguards of the kings and lords so it is better them to be used as a militia force to defend town centers.Or they can be called just like Jean darc’s troops.But then there has to be a hero like jean darc.
Poland
I dont have much knowledge about poland so I really want to hear ur opinionn about this civ.
Winged Hussars:Replaces Knights charges deals more damage than other knights
Genoa
Lombards,banks:In age of empires 3 there is an Italian civ which has lombards.Lombards works like a bank, you store some resources then the lombard multiplies it with interets in time.Lets say you put 1000 gold in lombard,it becomes 1000-2000 food or wood in some time.
Genoese Crossbowmen:Replaces crossbowmen,stronger than the normal onew also they have huge shields which makes them stronger against ranged attacks.Works similar to french crossbowmen.
Papal guards:A halberdier unit good against armored infantries,not bad against cavalry,expensive unit.Weaker against ranged units.
Condottieri:Replaces men at arms they get stronger near town center
Carroccio Tower:It is a wagon that carries a bell and the symbol of the city.Heals some units around it when units are idle.Cant heal in combat,cant transport units.
Stradiots:Venetian cavalry unit irl.Replaces horsemen they attack faster than other horsemens
Timurids
Variant civ to the mongols
Elephants:Same as Delhi
Elephant Artillery:Slow unit that carries a small artillery on its back.Has short range.I saw this unit in Medieval 2 total war and age of empires 3 so why not.Good against infantries and other artilleries except culverins and springald.Their range is shorter than every other artilleries.Culverins and cavalries can counter it
Tatar Horse Archers:Can not attack automatically like mangudai but do better against armored units.Also decent in melee.
Elephant units can be trained from age 4 wonder
Timur cant use hwacha and hui poei mongolian trebuchet
Aztecs
They have no cavalry but they have a variety of infantry
Jaguar Warriors:Replaces men at arm slow health but strong attack and fast attack rate
Jackal Runners: works like cavalry
Bone knight:High stat unit expensive
Eagle warrior:Javelineer good against armoured units and replaces handcannoneer
These are the ideas I thought while I was in a bus.They are not detailed I would like to hear yours to make a more detailed civ idea.