Very nice! I talked (~10y ago) at a Nix meetup to a company that did over the air updates of bicycle shed usage signs in NL that ran on embedded linux systems. One of their bigger challenges was that their downlink quota was very limited. I suggested them to peek at bsdiff, not sure if they ever got to it (or maybe would have gotten a better downlink ;))

I might give this idea another go myself with this nice rust library. With some heuristics one could partition the recursive closure of dependencies in a way optimizes for reuse (e.g. try to compute shared subtrees). Probably more efficient than a random tar of e.g. the entire root file system of a buildroot android system.