Great question and a part of the mod falls within the time frame.
Yes, many of the units especially the Gallic ones and Germanic factions units were involved..we are going to expand the units to better represent this time.
At the battle of Chalons in 451AD Aetius gathered his foederati allies, the Visigoths, Franks, Burgundians and the Alans whom a large group were settled in Armonica. The Visigoth King was alarmed at how small Aetius Roman standing army was for it was as it was probably mostly comprised of Auxiliaries, non-Italian troops, but from his stronghold in Gaul, he had gathered up his experienced field army of Gallic legionaries, and the surrounding limitanei: front line troops not as armed or trained as the legions, I'm sure. The question is how large of a Roman army did he have is quite murky.
"On the right wing of the Hunnic army Attila stationed the bulk of his Germanic allies. The Ostrogoths fought on the left, and in the center Attila took position with his best troops, the Huns. On the other side Aetius decide to put his least reliable troops, the Alans, in the center to take what ever assault Attila directed towards them. The Visigoths were placed on the Roman right, and the Romans themselves took the left. Aetius clearly hoped to execute a double envelopment, hitting hard against the two weak flanks of Attila's army while fighting a defensive, holding action in the center. When the Romans on the left were able to seize some high ground on the flank of the Hunnic right wing during an initial skirmish, they gained a considerable advantage"
So Now the Roman WRE was reliant on the foederati within their lands whom consisted of entire Germanic and once steppe factions and not just foederati trained within the Roman army as Roman soldiers. certainly a desperate situation that only a strong military leader such as an Aetius could do. Its also interesting to note that
Aegidius Domain of Soissons after Aetius was assassinated was able to hold Gaul secure even in his rebellion of Ricimers powerful grips on the WRE till he disappeared from history in 465ad
In 475AD a large foederati army, about 30,000 strong(the Scirian -Herulic )was stationed in Italy outside the cities under Odoacer. the foederati revolted and defeated Orestes, the magister militum with his standing Roman army. "After the revolt, the Germanic foederati, the Scirians and the Heruli, as well as a large segment of the Italic Roman army, proclaimed Odoacer rex Italiae" Odoacer -
http://en.wikipedia.org/wiki/Odoacer
All very interesting stuff