I think it might be a combination of his steely-eyed competence and how he occasionally seems to be emotionless, or at least not deeply affected by emotions. But yes, John + Android = Awesome.

I really wish I could commit to that story. I would honestly love to write it. But I'm trying to finish an original novel and I know your idea would end up being very long. I will definitely remember it, though. :D

In the meantime, if you haven't read my Scruffy A.I. Series (http://archiveofourown.org/series/14258) , that might give you a bit of an Android!John fix.