Here's a map of Danish dialect, the blue, brownish and yellowish are "Danish" dialects, the green ones are the "Jutish" ones and the red ones are the "Anglish" ones. Historical until 1850ties the "Anglish" ones had a border at Schleswig town. While the "Danish" ones include the 3 blue coloured names in Sweden. The spread of "Danish" Danish to Jutland are likely a relative "new" thing (as it have happen after the Anglo-Saxon migrations). The border between "Jutish" and "Anglish" have pretty much always been placed in South Jutland. The "Anglish" area are some of the most fertile areas, but historical the "Danish" areas always had a edge in population size. So even if the Angles had stayed at home, they would likely have been overrun by the Danes.
Thanks for the map, very illuminating! So if the Angles and other Ingvaeones don't leave wherever they are in Jutland, do you think they could've had the numbers to resist the Danes and/or counter-conquer them instead of the OTL turn of events? If not, then the OP would probably have to be achieved via more south-westerly areas as discussed. Though again, the idea of continental "Angleland" conquering *Denmark and taking their place as a major North Sea/Baltic entity is pretty cool. But hey, cool ≠ likely. *shrug*
If Aquitaine and Burgundy become one it would expand in NE Italy and E.Iberia and speak occitan/catalan, however it gets expelled in Iberia and Italy except for Piedmont and Catalonia on Age of Nationalism.
Works for me, especially since that means Occitan doesn't fade into relative obscurity like OTL. Considering that much of medieval troubadour tradition comes from Occitanophones, I find that kind of awesome! Then again, I like the language(s) of southern France vice northern
oil dialects, so sue me

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-Did I mention such a one?
I think whoever is by the Elbe will go Irminonic as OTL simply due to all the Irminonic speakers.
-The idea of a FrancoSaxon Empire is rather delicious

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As to pronunciation it's worth noting that Norman French retained W and Breton has no DH/TH. It's not quite clear why only the insular Germanic languages retained the dental fricatives of proto Germanic but even the European languages that developed them later (as position variants of dentals) are on the periphery than central Europe. Thus I'd suggest any dental fricative in a central European language to be a rare dialect variant adjacent to the periphery and an allophone rather than separate phoneme.
-Well you brought up how Frisia did see Angle immigration during the Volkswandering. I was pondering how it might've worked out if such a Frisia received those Ingvaeones who OTL went to Britain, and whether it would've meant a more resilient and distinctive NW Germanic nation, or been subsumed by other peoples.
-Of course, especially considering the irony of a Franco-Saxon empire taking the place of the OTL Carolingian Empire!
Moving onto pronunciation, I always thought that Breton's lack of DH/TH had mostly to do with overbearing Gallo-Romance influence rather than lacking it originally (using Cornish as a comparison); good point on the Norman "W". Regarding the European periphery developing DH/TH, European Spanish had a similar sound become standard (which, despite the common claim of it deriving from a certain king's speech impediment, developed organically and internally). Assuming a Franco-Saxon empire set-up, I could see such sounds become commonplace on the Armorican Massif (OTL Brittany, Pays de la Loire, and western Normandy) but not *Neustria/Austrasia. Hopefully I'm not too way off!