In the event of the surge of a unified pan-Germanic entity in the 7th century or so which would have not adopted Latin but opted to build a standard language (Koiné) based on the most spread Germanic dialects, how it would have looked like?
Certainly not close to current German, possibly a mixture of Low German-Old English with Danish traits?
For example:
Boermingshaem (Birmingham)
Hamburh (Hamburg)
Koelen (Köln)
Londoen (London)
Kaenterburh (Canterbury)
Winskaester (Winchester)
Aerhujs (Aarhus)
Utrekt (Utrecht)
Ideas?