Easy port came from a modder, and anything 'easy' in a modder's term doesn't necessarily mean 'easy' in the sense of us non-modders.

Also, what does BI offer, really? A horde or two, which did not happen historically. Loyalty would just be harsh on the Selucids. Night fighting can already be implemented, as RTR has demonstrated. Religions were all essentially Meidterranean apart from a few, and this would once again be mainly a Selucid problem.