hmm....i have a small idea. Marines. A pretty standard infantry, but with a high cost, cause he's created on ships. When created he garrisons on the ship, and you have a number of slots for like 10-15 marines. You can unload him close to the shoreline. It would be a great unit for naval invasions, and a great surprice tactic, but he would be expensive and medium strong to balance it out. I got the inspiration from reading some Osprey books about that era, and they depicted some marines from sparta, and persia, so i'm sure it wouldn't be so hard creating their looks I can find some scans anyways