In creating this thread, one of my primary motives was to carve out some general schema for the mapping of historical states and peoples to in-game factions that would allow a greater degree of representation ; not just for peoples, but for certain states that don't seem to fit in with the current s/p-to-civ mapping convention.
For example, the Ottomans are the Turkish civ in the game. But there have historically been many other important Turkish states in history, most notably the early Turkic Khaganates, the Seljuqs, the Tatar states etc. And because post-Khaganate Turkish history is inextricably linked with Persian, there are also other states similarly limited by the existence of the Persian and Ottoman civs: Ilkhanate (also related to Mongolia), the Ghaznavids, the Ghurids, the Khwarezmian, the Uzbek and Kazakh khanates, the Emirate of Bukhara, the Karakhanids... all these states just get elbowed out of the candidature due to the current restrictive schema.
Consider as an example the Ilkhanate. One might riposte that there already is a Mongolian civ in the game, but I would reply that the Ilkhanate is not satisfactorily represented by that faction. The same riposter (after the dogged, straightforward fashion of riposters) would then point to the Persian civ, but I could also point out that the Persian civ does not satisfactorily represent the Ilkhanate either (and has precious little room to do so either, considering it has to include Achaemenid, Sassanian, Safavid and Afsharid elements at the same time).
Now, the Ilkhanate might not be a high-priority civ for many, but I chose it as an example to illustrate the problems arising due to the exclusionary nature of the way civs are represented in the game. I am looking for a solution so that there is more room for states like the Ilkhanate to have at least a chance to get into the game.