Here is my design.
Bengals - Elephant & Gunpowder civilization
I personally want to represent all the three major religious faction - Buddhism, Hinduism and Islam. I think one can work with architecture and language for this.
Architecture
Regular buildings - Indians
Castle - ??? I’m unsure about this. New civs are having their own castles. Indians being the only civ with unique architecture have their own unique castle. Should Bengals get the same castle? I don’t think so. Can their castle be Buddhist temple like South-Eastern Asian civs? In that case, the central temple of Somapura Mahavihara can be used as a castle.
Wonder - Sixty Dome Mosque.
Language
Villager & Military - Medieval Bangla
Monk - Pali
King - Persian
Now let’s come to the main parts.
Civilization Bonus
- Get 20 free food every time a farm and fish trap is built.
- Monks can be garrisoned inside University to produce 10gold/min (maximum of 5 Monks per University).
- Demolition ships get +20% attack, +0.5 blast radius.
- Siege Engineers affects Cannon Galleon.
Team Bonus
All Elephants units +2 LOS.
Unique Technology
- Battle Elephants train 33% faster. (Cost - 400 wood, 250 gold ; Research Time - 40 seconds)
- Gunpowder units +1/+2 armor (Cost - 400 food, 300 gold ; Research Time - 45 seconds)
Tech Tree
Missing techs and units
Barracks - Supplies, Eagles
Archery Range - Arbalesters, HCA, PT
Stable - Bloodlines, Hussar, Cavalier, Camel, SL
Siege Workshop - SO, HS
Blacksmith - Plate Mail Armor
Monastery - Atonement, Heresy, Faith
Dock - FFS, Shipwright
University - None
Castle - Sappers
Eco - Two Man Saw
Unique Unit
Paik - anti archer foot archer
Cost - Wood 40, Gold 45
Training Time - 16 seconds
HP - 45, 50
Attack - 5, 6
+2, +3 vs Archer
+1, +2 vs Cavalry Archer
Rate of Fire - 2.0
Frame Delay - 23
Attack Delay - 0.7
Range - 5
Accuracy - 75%, 80%
Melee Armor - 0
Pierce Armor - 0, 1
Speed - 1.0
LOS - 7
Upgrade Cost - 950 food, 750 gold
Imperial Battle Elephants
Upgrade Cost - 1600 food, 1200 gold (1200 food, 900 gold for Elite)
Upgrade Time - 160 seconds (100 seconds for Elite)
HP - 350 (300 for Elite)
Attack - 16 (14 for Elite)
+10 vs Building (+7 for Elite)
+10 vs Defensive Structure (+7 for Elite)
Blast Radius - 0.4
Trample Damage - 25%
Melee Armor - 2 (1 for Elite)
Pierce Armor - 3
Speed - 0.85
LOS - 7 (+2 due to Team Bonus)
I personally feared that the free food from farm can be very OP in some cases. The instant food is like new Poles Folwark but you can build wherever you want. The amount is pretty smaller than Poles but it is completely free and is not subtracted from farm. Their eco will be one of the top right from the early feudal to late imperial. The Monk generating gold inside of University is not that huge imo as a Monk needs to be garrisoned inside for at least 10 minutes only to pay back his cost. This can be occasionally useful for the late game army combo which is very gold heavy for Bengals.
I tried to balance their OP eco by not giving them strong military bonus. In Castle age the only reliable unit is xbow which can not be upgraded into Arbalester in Imperial. So you need to switch to either Paik or HC later. Paik can be nerfed or TR can be removed if Paik feels too strong. Cavalry without Bloodlines is not that useful and no cavalier means using knights will be very situational like killing siege. Their late game army combo is very gold intensive as well as unconventional. I think this will make them play very difficult despite having great economy.