Musket, I entirely agree with you about the people whom one might not want to hear singing that song: I have also experienced the "heart sink" feeling referred to by DTM when certain people start singing it in a session. As for Joss Stone: even if she had done all the verses, it is pretty unlikely that she would have done it in "folkie style". I was not suggesting that only Eric Bogle could sing it, nor that anyone else who did should slavishly copy his style: but as others have said, there are only so many good versions out there (all a matter of taste, I know, as to what is "good"!)
And as for writing her own song: I saw a TV interview with her by the sea of poppies at the Tower of London, where she was saying how emotional she found it. Plenty of other people have written their own songs about WW1, from my great-grandfather who served with the Gordon Highlanders in France, to myself, and many others in between: so why do you think it so odd to suggest she wrote her own song??