I know three important accounts about them:  Battle of Thermopylae (480 BC), Battle of Delium (424 BC) and Battle of Nemea (394 BC) In the three, there is no mention of their panoply. The best we have is Thermopylae where Herodotus does not detail the Thespians' armor separately from the rest of the Greeks. He describes the Greek forces collectively using long spears and shields. During the final stand, he notes that after their spears broke, the remaining defenders (including the 700 Thespians) fought with swords (xiphē), and eventually with their bare hands and teeth.

according to understanding the new programming languages would make it easier to create a game from 0.

Is there any evidence of them being swordsmen?

And that's fine, because as @real_tabasco_sauce says, you don't want all your ships to be ranged units when garrisoned. Besides, shooting while on a ship is harder than from land, so that bonus is misplaced (maybe only if you consider ship towers). In any case, "arrow ships" were never a thing, this is a unit copied from Age of Empires, and Naval Oxybeles is a tech copied from Age of Mythology, when that's just mounting an oxybeles on a ship (fixing all that would enhance the game). I think one should consider the "arrow ship" as a ship with an oxybeles, with a decent range, and just remove that tech (besides, "siege ships" are usually equipped with a lithobolos). Additionally, one could have some light close ranged attack if ships are garrisoned, since realistically this should affect mostly crews, not ships (but right now the game doesn't deal with that, which I think it should, for both ships and sieges, to enhance the game further). There are many more things to be said about ships, but later on. Regarding swimming, some could, but not heavy troops.

Nobody ever remembers the Gracchi brothers.