I haven't played NW in ages, so I'm not exactly up to date with all the current bugs. However, I've been looking at the requests for new units and factions, and came up with a quick and easy way to implement this.
Deep in the cesspits of the
Skins & OSP Resources subforum, there are some wonderfully crafted skin packs that fully convert entire factions.
Raddeo's Duchy of Warsaw skin pack is the first that comes to my mind, but there are many others out there that can easily be turned into new factions. I do remember seeing a Spanish full conversion somewhere.
At the same time, you could also expand the current factions' rosters to include some individual skins.
Betaknight made some really awesome skins back in the day, and so did
Attila the Nun and
Marks. Those are the ones I remember, at least. I haven't looked at that subforum in years.
In any case, if you guys want to add new factions or skins, you won't need to make new textures and models. Just ask these modders if you can add their stuff to the game.
((Also,
shameless self promotion ))