Of course the BBC could announce that there was a problem with the phone lines for Louisa's votes as some posters have said, so they could bring her back for the semi-final and thus put three into the final which would help the ratings. (their main concern)
But "What are the chances of this happening?"

Ooh, I'm not sure oif they could do that though. I for one had no problem with Louisa's phone number.

Unfortunately, very low.

A new exiciting twist should be all dancing the same dance, with the same choregraphy ( designed by non related pro). This would then show who was actually dancing the best and could show how some stuff is being hidden by clever choregraphy by pros