Perhaps it could be implemented for more units. I think most ranged units could have a weak melee attack like in AOE3. Thureophoroi, Hastati, German spearmen, Celtic spearmen, Iberian infantry, could throw a single spear before melee.

Have you managed to get siege ladders working? (i cant test the mod right now since im on alpha 28) I think they could be available for all civs.

It is, at least on land units with persians immortals

I think the DE mod managed to have the Xiongnu champion cavalry switch bows and spears but im not sure.

This distinction might be partially due to gameplay limitations, i'm not sure weapon switching was implemented yet. So ranged and melee ships are separated.