If there was more dialogue to pull from Vader to make it work, I’d like that change. But it still sticks out unfortunately.
Even with the new series and they were able to get Earl Jones again, it be hard to imagine him saying “mother” … but there can be more syllables to pull from to make it. Who knows.
It doesn’t have to be Vader saying “mother”, just James Earl Jones. He’s said Mother !ucker in a movie or two, plus he read the bible for an audiobook. There are also a few great impersonators on YouTube. If Adywan decides to do it , he’ll have a few different options to try and make it work.