Wonders can unfortunately be the limiter to adding more Asian civs. Removing this mechanic is not an option, but improving it would be a good thing. Creating a brand new category of civs for Islamic nations would free Middle Eastern and Central Asian nations from the TAD DLC assumptions.
Civilizations like Siamese, Burmese, Korean, Vietnamese, Dravidians etc would have to be mechanically similar to civs like Chinese, Japanese and Indian (which should become Mughal civs) to keep Asian civs coherent - besides from those countries you can easily find a variety of buildings that can become Wonders.
Islamic civs, due to their distinct separateness and uniqueness, as well as their presence at the tripoint of Europe, Africa and Asia, deserve their own category in AoE 3. Ottomans civ are currently the only representative of this civilization circle (Hausa are Muslims, but above all they are African civs). The Ottoman civ got unique units to replace the ones shared with the European civs, so I guess that was a little preview that the developers were working on something in that area. I would be tempted to make the Ottomans civ even more unique - to get them reworked and become representatives of the Islamic category of civs. Below I will present my proposal for the rework of the Ottomans civ and in a moment it would be a simple representation of what Islamic civs could look like:
- Oriental House - would gain many variants of appearance. Houses built next to the Bazaar would provide slightly more population.
- Bazaar - replaces the standard Market. It could increase the efficiency of economic buildings in its vicinity.
- Spice Farm - would replace Estate. This building would be less efficient than its European counterpart, but thanks to Noria it would be much more efficient.
- Date Farm - would replace Mill. This building would be less efficient than its European counterpart, but thanks to Noria it would be much more efficient.
- Goat Pen - would replace Livestock Pen. Goats could be garrisoned in this building for passive Food production. This building would be less efficient than its European counterpart, but thanks to Noria it would be much more efficient.
- Mosque - This building, which is already unique to the Ottomans civ should become even more unique. I think he could have a Big Button that would provide an aura for a while that would increase the efficiency of all buildings. In addition, the Settlers could interact with this structure, so they would generate XP - it could be a praying animation. Also, this building would heal units.
- Caravanserai - This building is already unique to Indian civs, but I think it is a great match for Islamic civs. Of course, it should not restrict access to horse mounted units.
- Noria - unique to Islamic civs construction that increases the efficiency of farm buildings. This building can only be built after researching it in the Library.
- Military Academy - a building combining the features of the Arsenal with the Artillery Foundry.
- Wall, Trading Post and Barracks - I think this buildings could work similarly to the European equivalent.
- Oriental Harbor - a port building that has unique naval units.
- Shisha Roaster - a unique building for Islamic civs replacing the Tavern - because Muslims do not drink alcohol
- Minaret - a building that replaces the Outpost. Unlike Outpost, it does not attack enemy units, but it improves the efficiency of military units. It would have a much larger field of view than Outpost.
- Factory - this building could work the same as for European civs with the difference that they had their own model of the building.
- Library - This unique building for Islamic civs would be available from Age 1, and Islamic civs would start with the Library Wagon. This building would provide access to unique buildings (Noria, Oriental Garden), technologies and units that would be assigned to the appropriate “Field of Inquiry” - a unique Age Up mechanic for Islamic civs. It is in this building that the benefits of the various Age Up options would be used. This building would replace the Capitol. Age Up would take place in this building instead of the Town Center.
- Oriental Fort - it would be equivalent to a Fort, but could be built by Settlers. It would be less durable than a standard Fort, but would train units faster.
- Oriental Garden - This would be a building similar to the Cherry Orchard, but could be built by Settlers. You could choose the production: coffee is Coin, almonds are Food, indigo is Wood and Roses are XP. This building can only be built after researching it in the Library.
- Town Center - This building in Islamic civs would automatically slowly train the Settlers - proximity to Library, Minaret and Bazaar would speed up this process. Age Up would not be done in that building, instead in the Library.