I think they'd integrate well, I loved being renowned as a Gigolo, porm-star or Slaver, added more flavour to my character! I suppose some people even got a kick out of the Child killer perk too. Town reputations were awesome too, being vilified or idolized in different settlements etc.

Oh, I agree fully.

But now even Slavery and Slavers are no longer present in Fallout. I figured the Commonwealth would an ideal place for their business

I think Slavers could easily make a return to Fallout 4, especially for DLC. Wouldn't be hard to mock up a story about a mass slaver migration to the Commonwealth etc.