I have some sympathy for fake accents, being from Yorkshire. In my native tongue, the vowels are so short that there's nothing to build the notes around. You cannot really sing consonants because almost by definition they are stopping the flow of air, so all depends on lengthening the vowels to form the notes. We dont have long vowels where I come from, so there's little choice but to fake it. Imagine Geoff Boycott singing and you get the picture. My observation is that people tend to sing the song as they heard it: if it was Gaughan they copy Gaughan's nasal, aggressive sound; but would (try to) sing Marvin Gaye like Marvin Gaye.