This post is just for fun and some discussion of what we could add if we didn't had this unit limitation.
But I've added some new units on my own build, from another mod and I've enjoying a lot.
Some of the new units are Bruttian Swordsmen which are really needed in Southern Italy due to lack of swordmen units there. I also added a Syracusan Noble cavalry which gave more importance to Syracuse and Sikelian Hoplitai Haploi which again, allows the game to focus more on the importance of Sicily.
What units would you add if you add the chance? Maybe Athenian Hoplites/Marines?