Psiloi are a Hellenic unit so can't be built by the Etruscans, Phoenicians or Lydian/Persians. I should have added this to the read me really. I think the Peltast, Psiloi and Toxotoi are Hellenic only units. The Phoenicians and Etruscans will need to recruit (IE Bribe) mercenaries, such as Numidians, Iberians, Latins and Celts, as their skirmishers. If I remember correctly I made sure the cost to bribe these units was very reasonable versus building skirmisher types.