I think this is definitely on the right track. As you pointed out, the really hard part is devising a method for calculating the parameters in any such model. But for now, I'd like to put that aside and just focus on what the models might be.
Actually, what I really want might be a bit less academic than a formal model. I'd like to see a discussion that relates more financial concepts and terminology to software development. If we consider "technical debt" as some kind of loan, then who exactly is the lender and who is the borrower? What part of is the principal and what part is the interest? How does the "interest" compound? How are the "funds" actually exchanged between parties. What are the incentives for the lender and borrower to enter into this transaction? How do lenders choose the right borrowers? What are the risks for either party? How do parties hedge those risks?
Some of these questions seem to have intuitive answers at first glance, but I feel that they haven't been fully articulated yet. So as software developers, I think most of us really only have a superficial grasp of the "technical debt" concept. But I want to believe that our understanding can go much deeper than what we currently see in typical literature.
I don't have the answers here, but I'm eager to facilitate the discussion.