Currently I'm thinking of setting Crusades mod in 1220 when the Mongols have conquered most of Persia, so that I don't need a Persian faction but can still include Persian units (AoR recruitment system). Though the 1500 version will feature some Persian factions.

Thanks for the advice. I've also looked at the Broken Creasant mod for information about what Persian / India units the factions would have and what they should look like.