This has been part of the dpkg roadmap for some time now (https://wiki.debian.org/Teams/Dpkg/RoadMap). And something I'm slowly but progressively moving towards. But TBH it has been low priority. Knowing of projects that require it, and specifically which parts, or that are already using the static libdpkg library are very valuable, so that those parts can be improved.

If there's enough interest, my plan could be to expose just a subset of the current libdpkg as a shared library for buster.