Well that would be a few centuries before there was a Germany, so such early PoDs would de fatco be kinda dsiqualified by the ebutterfly effect, wont they?
Definitely. And it's rather easy to come up with such proposals:
1. The Romans hold Germania Magna for longer, effectively delaying Teutoburg by say a generation or two. In the meantime, technological transfer takes place to a much larger scale, making Germanic population significantly higher - and more civilized. In particular, there is a tradition of towns with Germanics.
2. Charlemagne in its fights with the Saxons wants to ensure that they get no supply from the east, thus he conquers the region between the Elbe and the Oder, takes a similar aproach as with the Saxons lateron, killing the Slav leaders, taking many Slavs into the proper Empire and resettling Franks between Elbe and Oder, thus Eastern-Colonization starts around 200 km further East.
3. The Eastern Frankish Empire keeps its hold on Pannonia and keeps colonizing it. Magyar invasions are defeated, the Magyars retreat over the Karpathians and follow the Huns into obscurity. With time passing by, Germans settle throughout Hungary.
4. As a defence of Northern Italy, a law is enacted which requires Germanic soldiers to be hired and settled throughout Venice and Friaul. This law becomes tradition, and in particular is taken over by the republic of Venice, resulting in gradual "Germanization" of the Terra ferma and some of teh Venetian colonies throughout the Med.
5. The great Slavic uprising is crushed decisively, many Slavs are killed and the area is colonized.
6. The Teutonic order manages to defeat the Lithuanians and colonizes not only Prussia, but the whole Baltics with German settlers.
7. Henry the Lion has a better relation with Barbarossa, and conquers Denmark, which ends in the HRE.
To conclude, it's rather easy to build a massive Germany with an early POD and liberal usage of conquest, cultural superiority and ethnic cleansing - the way large Empires evolve.