Realizing no one at my school does quite what I want to do
Seek an external co-advisor who can give you the guidance you need.
A co-advising arrangement can be a win-win situation: your advisor would still have you as a graduated student under his belt, the co-advisor gets to be a co-author of the resulting papers, and you don't have to seek a new position and deal with the complexities of moving and changing your living circumstances halfway during your Ph.D.
Candidates for being a co-advisor are researchers that are enthusiastic about the research problem and possess the required expertise. Examples would be the &quot;big name&quot; researcher and some of the other people who gave you feedback.