Mark, another good post. Only one thing I'd correct:

" I've read that, when the first roads were built, people in some remote regions still spoke in the manner of the original English settlers because their isolation had prevented any corrupting influences. Interestingly, the Brittish completely changed their way of speaking after those settlers had emmigrated. The original English accent was evidently something closer to that of the Gomer Pyle character on the old Andy Grifith television program."

This is an old canard that's been largely debunked. It was common in the early 20th century to romanticize the Appalachians and claim that folks there spoke "Elizabethan English," etc. The fact is, the language did continue to change, but it went in a different direction from English in England. So English in Appalachia preserved SOME older features (people say "a-going to the fair," just like in old folksongs!) which became uncommon in England, but England preserved other old-fashioned features (like the distinction between will and shall) which became uncommon over here. Thus Appalachian English can provide clues to what seventeenth and eighteenth century English was like, but you can't just say they're identical.

As for the accent, purely speaking no one knows. There are no sound recordings to tell us how Shakespeare sounded. The only clues become things like rhyme (what words were perceived to rhyme with what others). So relative traits can be determined to some extent, but the absolutes of what each vowel and consonant sounded like are lost to history.