Yeah, we could have them invade Spain and Aquitaine, and spawn Spain only if the Goths fell (they were conquered by the Moors) or they broke up into independent states
An idea then. Around 350 AD, Goths spawn as "Kingdom of Oium" in Southern Ukraine and Crimea (Also flipping whichever Crimean city exists to them), an entity unifying all the Goths led by a powerful Gothic king Ermanaric. Then the Hunnic invaders spawn at 370 AD as the barbarian horse archer hordes invading Gothic lands, and right next. Among the UHV goals of Goths there could also be "Survive the Hunnic hordes by seizing a city owned by the Romans", as these hordes should always be too overwhelming for a Gothic civ to withstand unless they go into the Roman territory, either by moving the stack of units they spawned with as a human player, or by having a conqueror event as an AI.
So then, if we speak about the AI, they invade both the Eastern and the Western Romans with the conqueror event at 370-375 AD and attempt to capture one Balkan and one Illyrian city. Then the Hunnic barbarian hordes begin pushing into the Roman and Byzantine territories proper, starting with 395 AD. Same with other Germanic barbarian units starting to break deep into the Western Roman territories, followed by the Gothic conqueror event on the Western Romans at 400 AD with them trying to seize a city in Italy and a city in Aquitaine. Then, once succeeding, they proceed to take over the Roman Hispania. By this time it is likely that the Western Rome would also already be collapsed.
Somewhen at around early V Century, a Hunnic civilization could finally spawn with the capital city in modern Hungary and the Southern Ukrainian and Crimean cities flipping to them, which would later proceed to represent the Turkic Empires in Europe, not just the Hunnic Empire. Then they also get the conqueror event attempts at the Goths (In case if they own any cities in the Balkans, in Illyria or in Italia), at the Byzantines and at the Western Romans simultaneously. The Hunnic Empire may later change to being the Avar Khaganate centered in modern Hungary.
Now I also think, maybe Hungary could be its own civilization as well? It seems to fit in as well, just like Bulgarian civilization, with this larger map. They're usually always represented as the spawning independent city of Buda which tends to always fall quickly to either the Holy Romans or the Byzantines soon afterwards.