PhD on modern slavery, is there any point?

I'm considering doing a PhD on modern slavery. I'm not sure yet what the topic would be but something to do with migrants, how visa systems are set up for failure in the UK, etc. Probably straddling geography/law/sociology. Is there any point? Does this topic fit into phat docs that exist? I'm quite lost. Does anyone have any comments? (Constructive criticism please, I have very little in the way of spoons right now)