This topic comes up for discussion periodically, and I can sum up the responses for you:

1) Never sing in anything but the voice and accent that are natural and native to you;

2) Always affect whatever voice and accent you think fit a song;

3) (to be read in the voice and accent of a certain previous poster:) Do whatever it takes to be successful in the music racket.

No end of reasonable and not-so-reasonable arguments have been presented in support of these views, so if you're like most people, you'll choose the arguments in favour of what you're inclined to do anyway ....

FWIW, in my opinion, this world could use a few more Chinese-Australian Calypsonians!