User blog comment:Powerhouse411/Who Are Your Choices of Shichibukai?/@comment-24070327-20140206091849/@comment-4759107-20140207125610

I'm not sure I can see Kai working for the WG, unless they gave him free reign to kill all the Tennryubito who were part of Tartarus. I'm sure he and the Seraphs would be good at it, but given his past with them I can't see him joining up.

It's an interesting thought though :)