To add to the subject, according to
wikipedia, the "Suebi" who participated in the 406 "
Crossing of the Rhine", along with the Vandals and the Alans (and probably the
Burgundians), were a tribal alliance consisting of the Marcomanni, the Quadi and the Burii. Considering the fact that early Roman authors consider the "Suebi" a loose super-tribal grouping rather than an actual tribe, this seems very likely. This view is also supported by archaeological evidence. From
wikipedia:
"
After about 400, the old cremation burials typical of Suevians like the Quadi disappear in Bohemia."
This would imply that the migration was relatively thorough. It seems the tribes departed in massive numbers. After the migration, their former territories were largely taken over by the Rugii, the Langobardi and the Gepids.
As for the "Alans" of Western Europe, who took part in this crossing, I question if they were directly linked with the Eastern Alans who were the vassals of the Huns at this stage. If you look at the geographical location of the migrating tribes, the Suebi confederation occupied modern Checkoslovakia and the Vandals were located northeast of them, in Silesia. The Alans who were part of the alliance probably came from the Hungarian Plain.
Now, we do know that the Iazyges had previously occupied this area. In a
thread in RomanArmyTalk, Alanus states the following:
"
Iazyge culture changed at the end of the 2nd century when the Roxolani moved onto the Hungarian Plain; and both tribes, now intermixed, were given the designation of "Sarmatians," a name which lasted into the latter 4th century. According to Harmatta, the Roxolani introduced the longer Alanic sword."
As the name "Roxolani" means "White Alans", it isn't unlikely that this tribe (along with the former "Iazyges" as the two groups had melded together) formed the western "Alans" of the early 5th century. Although it is likely that scattered elements of the eastern Alani had joined their western cousins, the western Alans were definitely a different political entity than their kinsmen under Hunnic domination.
In game terms, if you're looking to recreate the historical situation of 395, the Suebi should probably be settled where the Quadi currently are, and represent the confederation of the Marcomanni, Quadi and Burrii. The Roxolani and the Iazyges should be merged into one faction, south of where the Quadi are now, and a separate entity from the eastern Alans (either make them the playable "Alans" or use the name "Roxolani"). The Lugii should probably be replaced by the Vandals (since the two were the same entity), who were still settled at this point.
This would leave the "Marcomanni" location free to be occupied by another Germanic tribe (probably the Burgundians, at this date). Ultimately the map isn't going to be perfectly historical since the provinces and regions are fixed as CA made them, and it won't be possible to accurately represent the location and territory of every tribe, as many of them were in reality occupying territories smaller than an in-game "region" and you'd have to put several tribes in the same region.