Well, according to the Daphne Parade and other sources, the Seleucid Army was, during the time of the Empire's war with the Egyptians, called "The people's army" because it was based almost entirely of milita thureosphoros, which must have had not just Greek but native troops as well. As for native archers, the Seleucids logically HAD to use native archers, because Greeks (aside from Cretans) aren't known for their archery. Most of the light skirmishers were native, because a lot of greeks saw skirmishing as a job for the "lower peoples" while they fought as thureosphoros, thorakites, cav, and obviously, the Syntagma/Phalanx. So while I do agree with you, native melee troops is a bit unreasonable, the roster I am working on (slowly, I grant you that) uses native troops for almost only the skirmishing/archer arm, with the exceptions being Dahae Horse archers and Median cav, but at least the Median cav, and the native peltast have Greek/heavier counterparts in the roster for Greek purists like me.