Hi Morwen, like I said before, I wouldn't recommend that you do what you're trying to do in any way - other than the way that you find it works for you.
When I said immerse yourself in the music rather than consciously mimicking performers, I was aiming at avoiding making your singing sound like a tacky racial pastiche. And in fact I believe, from the what you say, that this is what you would wish to avoid.

"And what about "Day Dah Light (the Banana Boat Song) which uses a lot of dialect? I think I'd keep the dialect, for example, "Come Missa Tallyman, tally mi banana", but pronounce it so that I sounded Australian with a distinct Jamaican inflection. It is very hard to sing a song written in Jamaican patois without adopting the inflections."

Sounds to me like you have worked out how to make it work for you..
I like your argument for the Baez performance btw.