The idea I had with the Croat unique unit (the Zupan, though Ban would be acceptable, too) was for it to be a light cavalry unit that’s strong against the Spearman line. They’d still be weak to Camels and Genoese Crossbowmen, as well as being less adept at defeating archers, but they’d cost much less gold than the Byzantine Cataphract and protect their primarily infantry and cavalry-focused land army.
I also thought the Croats could have a second unique unit, the Kondura, as a naval trash unit with bonus damage against the Fire Galley line.
The unique techs I had in mind for the civ would be, firstly, a technology that reduces the gold cost of the Knight and Zupan lines, and second, a technology that improves Castles’ strength against Battering Rams, since the Persians no longer have Boiling Oil.
To me it seems like you are fully biased in selecting civis,which is ok since this is your mod concept.You have polynesians added which had little no value in the middle ages as per your own thresholds.
Im still looking in to croatian military but could not find anything yet.
This mod might have something for you
Since there are no Oceania civ in the game and satisfying the empty of the region of the world is the first goal to add new civs. Not bia as you said.
In the fact, I had not put Croats and Gokturks into my list in the beginning. I decided put Croats in since I found that it can have a very special tech tree with great navy and cavalry unlike other in-game civs and have the campaigns with many in-game civs after I started to research its history of the warfare and the Balkan culture. In the same reason, I put Sinhalese down after I researched it. I cannot be persuade by myself to add an another elephant-navy civ while Bengals is already there.
Even now, I have no any emotional feeling to Sinhalese, Croats, Polynesians, Siamese and other civs on the list. Accusing me of being biased may be your preconception.