Like you say, modeling the interface between the shared library like a Thrift struct (which can be serialized) may be beneficial, and would facilitate adding/removing fields by having e.g. default fields. Or just crash if a non-backwards compatible change is made, e.g. a new field is expected but not present, but ignore fields that are present but no longer expected.

I think the other killer feature that this is missing is being able to have a "release" compilation mode that removes the hot reloading entirely, and seamlessly statically links in the library.