So I'm thinking about how to bridge the two worlds.
I know that Godot exposes a C API, so once I get the new compiler operational, I can likely write and control subsystems from there.
I could do a project in GDScript/Nodes natively and just cover the parts that I can do for now, bootstrapping a setup that we can build upon.
And then later we can rewrite select systems, with the benefit of hindsight, in the custom compiler and add more shared libs to the project.