I was going to suggest more unique units, especially the “Khorasanis”, especially the “Abna al Khorasan” for feudal. Let it be unlocked by the technology from the military headquarters, or it could be from the commercial one as mercenaries (at least it would be better than the technology that only gives them more resistance to merchants). They were also called Shakiriyya.
There are also others, like the Daylamites, or the Hujariyya
New Technologies
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Khurasan road/// Black Standars soldiers.- To unlock the khorasanis swordmans, or khorasanis cavalry.
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Ceramic Grenades.-** Also some technology to replace torches with “Naphta Grenades” (not Greek fire, nor explosive, but highly flammable).
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Arab Horses.- Another could be something to “improve” the light cavalry, which in theory “should be very good,” given the famous “Arab Horses,” or the Arab-Berber mix, which they supposedly used to defeat the Byzantine armies several times.