I know that this is a more delicate and problematic proposal, given some historical aspects of the Goths and gameplay concerns. First, the Goths were a semi-nomad people and this condition is hard to represent in game. They also had a relatively short (at least in game terms) trajectory: they appear in historical record by the 3rd century CE and their successors disappear by the time of Moorish invasion of Visigoth Hispania (711). Another issue is that could make things messy and unbalanced in early Medieval Europe. I vaguely remember Leoreth being against moving the French spawn date to represent the Franks for gameplay reasons and that in the original Rhye's mod the early spawn date of France was moved to later given some issues. All things considered, it may be better to leave the Goths (and other Migration Period peoples and entities) represented as barbarians units and indy cities, however I think that their addition, if well thoght and implemented, could be really cool and fill the gap between the classical and medieval civs in Europe.
Spawn/Location: 180 CE/Black Sea coast
Although we have some evidences for early Goth migrations, I think that the spawn date should be around the time that they came to the Black Sea, the late 2nd century CE. Giving the short timespan of the civ (and the need to squeeze many turns as possible to make the civ viable), I suggest 180 CE, the end of Marcommanic Wars, which was one of the first large populational movements in the Migration Period and when several Germanic tribes were pushed South and East. The starting place could be the semi-legendary
Árheimar, indentified with Dnieper river and can be autorazed on conquest/collapse, or
Theodoro (or Doros), the Crimean Gothic capital that was settled with them in the late 5th century.
Leaders:
Cniva, Alaric and Theodoric, the latter two depending where is locate the Goth capital.
Color/Symbol: Black or Grey/ the
Visigoth eagle.
Expansion stability: core intially in Western Black Sea coast and Crimea, shifts to Northern Italy and Northern Iberia/Southern Gaul when cities are conquered/founded in these regions. Historical in Dacia and Pannonia, Italy, Iberia, Southern Gaul and few titles in North Africa.
UP:
Furor Teutonicus (military units have + 15% strenght when attacking; starts a Golden Age when conquers an enemy capital)
UU1:
Gadrauhts (replaces Swordsman, can heal when pillaging).
The name is "soldier" or "militiaman" in Gothic language. Represents the Gothic infantry tradition. The unit capability of healing when pillaging would help Goth players in their conquests (making quicker have full strenght units) and also mimics their historical raids and plundering (the Goths razed the Temple of Artemis, for exemple)
UU2:
Druhtiz (replaces Horseman, + 25% strenght against Melee Units).
The name is the Germanic nomenclature for the Latin
Comitatus, an armed retinue that was common in the context of Germanic warfare. This practice is a direct source of feudalism. The idea here is to represent the powerful Gothic Cavalry without using a generic "Gothic + Horseman" name.
UB:
Hermitage (replaces Monument, bonus culture when the city has a religion and offers a Artist slot) or
Hov (replaces Pagan Temple, a small bonus when producing military units)
I confess that is really hard to find an adequate UB for the Goths. After their nomadic phase, the Ostrogothic Kingdom lasted for only few decades and didn't leaved a big architectural legacy (in fact, they mostly tried to restore Roman buildings) besides the Mausoleum of Theodoric. The Visigoths lasted for much longer, however there are very few buildings that still exist and basically all of them were small churches and chapels. The
Hermitage of Santa María de Lara is probably one of the most remarkable Visigoth buildings still left, so we can use the hermitage as an UB. The other possibility is the
Hov (or
Hof), used by other mods and that represents an Germanic pagan sancturay.
UHV:
The Ostrogothic Kingdom: have a capital in Italy and control three cities in Italy, Illyria and Pannonia by 550 CE
The Visigothic Kingdom: have a capital in Iberia or Gaul and four cities in Iberia, France and North Africa by 700 CE.
Gothic Codex: Be the first civ to discover Feudalism and produce 2000 culture by 800 CE.
The UHV are pretty straight foward, representing their invasions on the Roman Empire and establishing new Barbarian Kingdoms, while the third is focused more on the cultural aspects of the Gothic legacy, particularly their contribution to the development of legal systems in post-Roman Europe.
Notes:
* to make the Goths a more viable civ, we could postpone the spawn of the Spanish from 722 (founding of Asturian Kingdom, actually under leadership of a Visigothic noble) to 910 (founding of Kingdom of León), so we have more turns of gameplay.
* if the Goths are really included in the mod, we could consider making the French spawn earlier to represent the Franks and make the early Medieval Europe more interesting.
* most of the art required to make the civ is already done in other mods, so we can borrow some to make this one.