I'm temped to do politics and phonetics, comparing far left and far right, but I'm not sure I'd be able to adequately control for regional differences for the different data points. Also, I'm not sure what data points I'd be looking for in their speech, as I'd be looking at unconscious markers instead of using [ing] or [in] in a debate.
I've been think about doing how phonemes are borrowed from one language to another, but I'm not sure whether that's the type of project he'd be looking for. But on the other hand, my thread language could be Welsh, with other examples pulled for different sections.
I think I'll have to look though my Sociolinguistics text book to see what strikes my fancy. I have to see how far I can get with only written materials, as my hear for transcription is horrid.
I'm also amused/frightened that doing a "Who would you cast in a movie of your life?" meme has inspired a short story. Dunno, but it's about trying to break up with your girlfriend by knitting a sweater.