Lynores, just marking this down so we don't forget & since I bug you too much in PMs.
I think it'd be a good idea to add a Phoenician (or Liby-Phoenician) marine to the Carthaginians. I was reading back and remembered you remarking about the Athenian's archers being put into the backmost ship during a sea battle in order to give them an extra edge in naval affairs, and it reminded me of Carthage's own predominance in that area within the Western Mediterranean. It wouldn't require any new material, just a various allocation of resources.
The context for it is various secondary resource commentary on Phoenicians being some of the primary marines of the Persian fleet (along with Egyptians and I imagine loyal Ionian Greeks) and primary visual depictions from I believe Carthaginian settlements in spain of Punic marines in linothoraxes (with vertical quilting, but that's not necessary). Now in the context of those visual depictions they are armed with smaller than an aspis round shields and probably javelins. We could arm them as such, or we could suppose the Phoenician origin of the Carthaginians would allow for the use of the bow. That might be better from a gameplay perspective and isn't a terrible assumption - I read somewhere the same assumption of Carthaginian 5th or 6th century charioteers using bows (rather than javelins or lances) in the Phoenician/Assyrian tradition.
My thoughts for equipping options are:
1) Replace the Libyan Infantry with "Liby-Poeni Marines". Keep the tunics, keep the javelins, keep the shield (Probably try and limit it to Numidian shields that look more 'sturdy'), add a helmet, remove the spear and give them a sidearm instead. We'd then have a "Poeni Marine" unit upgraded from it, wearing a linothorax, with the Numidian shield, javelins, sword, helmet. This would be the Carthaginians Domestic Peltast tree.
2) Create a new unit (offshoot from Libyan Spearmen) of "Poeni/Carthaginian Marines". Plain linothorax, helmet, bow, sidearm.
Two more stylistic and aesthetically pretty examples of Phoenician Marines. These aren't intended to represent them in the most historical context (There's some other artwork I'll upload which does a better job), it just looks neat. I do really like the 'frilly' edging of the tunics and the folded one over the other style of the bottom of the linen skirt beneath the padding & linothorax.
http://www.aeroartinc.com/phoenician-marine-holding-spearshaft-and-spears.html
http://www.aeroartinc.com/phoenician-marine-in-alternate-uniform.html