If you're interested in securing software update systems, check out The Update Framework. TUF is the only system I'm aware of that has a comprehensive threat model for the problem of securely distributing software updates.
TUF also attempts to address a set of problems that some systems don't need to solve because it isn't a need they have.
With that said, I would agree that TUF provides a great model.
I'm not sure how connected to the project you are, but if you're aware of where I might find that, I'd be very thankful for a helping hand.