Can Messy Topics Make Clean Dissertations?

I'm in the struggle between finding an interesting dissertation topic that will propel me through the end of the process and one that I can put a neat bow on within a "reasonable" time period. To that end, here is the beginning of some thoughts ...

• Historical lit review / historical context of Open Education: Chautauqua, Open University, Wedemyer's Learning at the Back Door (sociology of nontraditional learners)
• Questions? Open education - Internet meets Chauaugua lecture series?, Motivations of learners, strategies used to support, quality of communication, university extension programs, content analysis - do non-credit vs credit differ, quality of feedback, quality of artifacts, business model, sustainability, blurring of lines between non-traditional and traditional?