As much as I'd like a true Medieval Age, I don't see the need to have a separate Western Roman Empire and an Eastern Roman Empire. I think a single Byzantine civ would be enough. Then the Ottomans could be in Exploration.In the spirit of the Pirates' Republic - where the loose-ish temporal and conceptual boundaries of these Ages establishing a degree of speculation - a true Medieval Age (against Antiquity and Exploration) would also have room for a true "Western Roman Empire" as if it had survived Odoacer AND a Holy Roman Empire AND a Justinian Eastern Rome. Meanwhile Exploration could present a "what if" Byzantine power.
The fall of Constantinople is one of the dates that historians look to as the end of the Medieval Age after all.
In regard to the Khmer, that could at least allow them to have a religion, something that they are known for but currently unable to have due to them being in Antiquity.Far better to have some civs in the "wrong" era than to have eras that are forced into the game without any gameplay concept to build around.
