They tried something like that on the Bakerloo Line with the PIS showing 'STAND BACK TRAIN APPROACHING', but it didn't really work. The game has improved now, it must be possible now... Actually, I don't think they said it was impossible. I can't remember what they said...
I really don't like the generic announcements for UK routes, the voice is hardly realistic, I think the only case where they've got the right voice is on Cathcart circle where a Scottish voice is used,
