Jim and Dan, you (not surprisingly) raise very important points. Dan, your point about whether these elements of citizenship cohere is one that I've struggled with. On the one hand, it could be argued that this could be tested empirically (e.g., factor analysis). On the other hand, highly related, yet theoretically distinct constructs could give the false impression for an overarching construct (e.g, factor analysis). As an example, I recently reviewed a journal article that was focused on testing for an underlying civic engagement and civic identity factor - that is, that civic engagement and civic identity are two components of a latent construct (as well as having second-order factors). I was very critical of the paper because I did not see a theoretical basis for conflating these two concepts - rather, previous research and theory would suggest that engagement helps in the formation of identity and that identity would then lead to future engagement. At the very least, a stronger theoretical argument needs to be made for this proposed cohesion.
I think Jim's point about commitment is consistent with Dan's point about there being cognitive, emotional, and motivational components of an identity (and consistent with Erikson). My proposition of CARE (again, very much thrown-out there to start a conversation) is based on such a model - i.e., identity having cognitive, emotional and motivational components, though, based on your comments, I think it's possibly lacking.
What I wonder, then, is how would one empirically be able to assess a developing civic identity - not necessarily that there is a linear progression but that there might be qualitatively different levels of a civic identity (building off the general frameworks of Erikson, Marcia, Waterman and the more specific ethnic identity frameworks of Phinney, Sellers).
The tension is between getting specific enough to make such a framework meaningful (e.g., putting meaning behind "civic") and making it broad enough to capture the commitments made to a diversity of civic processes (to Jim's point).