Checking out the two elite kits available it appears to me that Seamus is featuring an Irish accent when speaking, adding flavor to his character.
Now when I listen to Ernst - being from Munich, Germany myself - no Bavarian accent/dialect at all!!! What I heard so far is a German voice speaking a bit with a very dramatic tone in the voice. So since new voice recordings have been made, why not using some local accents on the Axis side as well? An axis soldier cursing in dialect would surely be a nice touch to the elite kits.
I think the main goal of this BF is to use English voice overs only? Therefore original languages are not available?
All BF versions (if I am not mistaken) since 42 had an option for a setting where you were able to choose the non-english speaking fractions speaking in their languages as well.