Tell me how to do something worth doing with ETH and I'll be impressed. Cue the intellectualization from "investors."
It could detail in code the principal, functions to trigger interest rate increases/decreases, functions to cancel, early termination fees, payment addresses, max payments per year, end dates, and whatever else a mortgage contract would need.
As a developer I would have felt much more comfortable with that than legal papers, brochures and pamphlets.