What sort of genre theory?

One thing my committee has asked for is a more explicit theoretical discussion of genre to form the basis of my characterization of spectacular personal reportage. I recall a fellow PhD student presenting her genre-studies-in-progress and saying: 'If any of you have been thinking about studying genre as such, I advice you not to do it... I'm serious...' And I have in fact kept discussions of genre theory to an absolute minimum, but made sure that I point to Carolyn Miller to express my trust in her

rhetorically sound definition of genre [which] must be centred not on the substance or form of discourse, but on the action it is used to accomplish. ("Genre as Social Action", 1984, p 84).

With my general focus on rhetorical agency, I have attempted to characterize precisely the social action which my particular band of reporters make such spectacular efforts to accomplish through personal recordings of their field trips. I read one or two reporters and one or two texts at a time, and I qualify their participation in the genre as I go along, but it's true that I haven't defined in any strict sense what is, for instance, a sufficient criterion for participation. And I wonder if I'm being strategically vague about it to spare myself some work, or whether I really don't find the more strict approach fruitful? Genre theory won't become fruitful by itself, I know, but if I ought to put work into it, I am simply wondering where to begin and for what reasons.