If there was a RTW 1.6 Patch, what would you want in it?

[Ludens]

Shield Wall is hardly a phalanx like the greek ones, take out the phalanx and give them better training and defensive strenght if you want to be accurate.

The first Persians were steppe nomad, so the Parthians are indeed true Persians, as for the Imortals they were revived many times like this article states, although you are correct, since the last true immortals were defeated in 333BC and this game starts almost 1 century after.

I don't quite follow your logic. Both the Parthians and the Persians were steppe nomads, so the Parthians are Persians? Anyway, the Persians had ceased to be steppe nomads around 8 centuries before the start of the game. The immortals were revived by the Sassanids, not the Parthians, and as a cavalry unit, not an infantry one. The cavalry immortals are included in BI.

I agree that BI's shieldwall would be a better way of representing the German formation than the phalanx. However, the unit is not fictional: Germans used lances and dense formations. It doesn't require a genius to realize spears are more effective in a block.