Dissertation Idea #2: Behavioral Theory
Taking everything that psychologists and behavioral economists have learned about how utility actually works, and build a relatively realistic utility function. Then plug this utility into several classical theoretical results and see how they are affected. Of course, economists refrain from using realistic utility functions because of mathematical intractability as much as lack of knowledge about what they look like, so this may be a doomed project. Hard to know for sure without losing a few months of life to it first.