Neat concept.
Consider:
Aztecs: Otomi - Melee unit that attacks at range. Start with French throwing axeman, but instead of axes it throws rocks. Not a slinger - just deals base damage with no bonus of any kind. Same stats as elite throwing axeman, but with 10 less hp and no bonus damage. Gains +1 range from atlatl, but not a second projectile. Available in age 4.
Bengalis: Flail elephant - unique upgrade to siege elephant. Available in age 4. Grants + 20 class armor from siege weapons, +40 damage vs siege and heavy siege, and increases speed to 0.7.
Britons: Dismounted Knight - Champion replacement. +1 attack, and +2 melee/pierce armor. Bonus damage of +6 vs hussars. Available in age 3
Bulgarians: Baghatur - Unique hussar variant. 5 less hp, base attack of 10, 1/2 armor, +5 vs building and villager, no bonus vs monks.
Burmese: Royal Battle Elephant - Grants +50 hp, +4 attack and improves blast damage to 0.5 tiles (33%). Available in age 4.
Byzantines: Limitanei - Additional spear line unit in barracks (generic spear line NOT replaced). Available in age 4. Lower bonus vs cavalry, but better attack rate and pierce armor. Attack rate of 2, 7 attack, bonus +15 vs cavalry, armor 1/3, speed 0.85, cost 45 food 5 gold. Benefits from gambesons.
Celts: Ranger - Unique arbalester replacement. 60 hp, 6 attack, 6 range, 1/2 armor, 0 frame/attack delay, 100% accuracy, benefits from civ infantry speed boost and gambesons.
Chinese: Sea Hawk - Unique fire ship replacement. Has 10 ship armor and extra +5 line of sight.
Cumans: Camel Lancer - Unique upgrade to camel rider. Bonus vs cavalry remains at +9, gains +9 cavalry armor instead, gains + 0/2 armor.
Ethiopians: Tamed elephant - unique battle elephant line. Available in age 3, upgrades to elite. 400, 500 hp;14,16 attack with 33% splash in 0.5 tiles; armor is 0/2, 0/3.
Franks: Kings Paladin - Unique paladin upgrade. Grants +5 bonus vs infantry.
Georgians: Crusader Knight - Unique cavalier replacement. 100 hp, 4/5 armor, 16 attack.
Goths: Saxon Raider - Penultimate militia line upgrade on top of champion. Trades sword for 2 handed axe. +10 hp, +1 attack, and +6 vs buildings and villagers.
Huns: Shaman - Unique monk replacement. Has +20 hp and moves at 1.4 speed.
Japanese: Flaming Arrow - Unique scorpion upgrade. 50 hp, 14 damage, 0.8 movement speed.
Khmer: Village Guardsman - Additional spear unit in barracks - does NOT replace basic spear line. Costs only 55 food and takes 0.7 population. Less effective vs cavalry, but excels vs elephants. Spearman with 40 hp, 4 attack, +16 vs cavalry, +11 vs camel, + 50 vs elephant.
Magyars: Black Rider - Heavily armored horseman, good vs ranged units. Monaspa stats, no regen, 2/8 armor, 1.45 speed. Unique stable line, starting in age 4.
Malay: Cetbang galleon - Galleon upgrade. +4 pierce damage, +4 vs ship, +12 vs buildings, and +5 ship armor.
Malians: Donso - Additional skirmisher-type unit at archery range. Does NOT replace basic skirmisher. Costs 35 food, 20 gold. Skirmisher stats, deals + 2,3 vs cavalry and camels, +6,9 vs elephant, +2,4 vs infantry, nothing vs archers.
Mayans: Feathered spearmen - Penultimate spear line upgrade on top of halberdier. Grants +2 attack and increased movement speed to 1.2.
Mongols: Laminated cavalry line - Upgrades scout cavalry → Laminated Cavalry (light cavalry, but with +1 melee armor) → Heavy Laminated cavalry (laminated cavalry, but adds another +1 melee armor) .
Saracens: Hakeem - Unique monk upgrade. Available in age 3. +30 hp, and rides a camel. Itself and units being healed are immune to conversion (even the heresy death thing).
Sicilians: Carrack - Unique galleon upgrade. Available in age 4. Same stats as Elite cannon galleon, but has speed of 1.35 and 14 range.
Slavs: Cossack - Additional barracks infantry unit. Weak melee unit that fights with sword. Costs 45 food, 10 wood. Available in age 3, upgradable to elite in age 4. 55,60 hp, 5,6 attack with 1.7 attack rate, + 8 vs spearmen, +2 foot archers, 1.2 speed.
Teutons: Dragoon - Stats of an Arambai, but shoots bullets like a conquistador. No bonus damage. Armor classes same as conquistador. Range of 3,4, accuracy of 20%,30%.
Turks: Cebelu - Replaces camel line. Available in age 3, upgradable to elite. Steppe lancer-like unit, swapped armor (2/0 instead of 0/2) +9 vs cavalry and camel, +15 vs elephant. Elite upgrade gives +1 melee armor and +12 class armor. Benefits from sipahi.
