Hi,
I think overall the Ottoman depiction has been extraordinarily done, mainly thanks to the presence of unique units (Janissary, Great Bombard…) that carry unique designs.
Indeed, the Cavalry Archer (shared with the Russians), Janissary, DE Great Bombard, Galley, Nizam Fusilier are just perfect and faithful representations. Below are comparisons between historical reconstitutions or evidences, and the in-game models:
Janissary
Great Bombard
Cavalry Archer
Nizam Fusilier
Abus Gun
Galley
The Sipahi unit however looks too lightly armored: given how powerful it is, I believe it would’ve been more pertinent to base the model on the finest Sipahi regiment, that is to say the Kapıkulu Sipahi. AoE4 actually chose that depiction and I think it is superb and more coherent.
Sipahi
For the other regular units, including the Royal ones (Hussar & Grenadier) that unfortunately don’t have a special design distinguishing them for the other civs’ counterparts (an issue shared among all European civs), the Humbaracı (Grenadier) and the Bostancı (Hussar) definitely could enjoy a unique design.
The picture you chose of the 3 men (with the singular long black hats) are indeed Humbaracı and would be the ideal design for the Royal Grenadiers!
Same for the Bostancı, with the typical beany, you did choose the right picture too!
Progress could be made on the other regular, non-royal units, that is to say the crew for the remaining artillery units (culverin, falconet, mortar, horse artillery). To improve that, maybe the crew model could re-use the DE Great Bombard’s crew model, or use one of the following:
Regarding their navy, the galley is a wonderful addition and so are the crescents replacing the crosses on the sails (like the Indians). Other than that, Ottoman navy relied on galleys of various sizes and ships that followed the generic European models.
Galleon
Frigate
Battleship
Therefore, I only see the Sipahi that could enjoy a reworking, perhaps drawn on the new AoE4 model, and the artillery crews.
I think we must be very careful by what is meant by ‘islamic’.
Ottoman style was quite unique: as shown with the pictures above, the AoE3 representation is quite accurate regarding the units.
As for the architecture, I’ve wrote about that here and there and proved AoE3 also offered an appropriate depiction. Only the houses could seriously enjoy a redesign (AoE4 presents a new, pinpoint model) and the male settler.
House
Settler
Outside the Ottoman roster, several new units wear Ottoman-influenced clothes, concurring with reality, like the Pandour, Shock Cavalry, Winged Hussar…
Best,