So I came to a conclusion when listening to the lecture I attended on HTML5.
One of the speakers made a comment regarding accessibility in general:
'It doesn't have to be exactly the same, it just has to convey the same meaning... essentially... people shouldn't be missing out on anything...'
I've decided to take this approach with some of the interactive subtitling... the VO's whilst being long, don't really need to be subtitled to the letter, I just wanted to mix it up a bit, without discounting people who can't see the screen, they get the VO, people who don't want sound get the subtitles, everyone's happy. .. i'm close to finishing now... exciting times!