its a pain to hold taras, but its possible, and if you take good care in battles not to lose your elephants, you can take rome as early as 267 + whipe macedon of the map. this requires you to make a peace with KH tho.
the factions i had most fun blitzing with were KH, Pontus, Pahlava and Adeui. The first 3 are rather easy (specially parthia, you can take the entire eastern part of the seleucid empire withing a decade by using FM) if you know what you are doing. Adeui is actually a big challenge. I never read your guide, but i basically did exactly what you did haha.
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