Compile the engine from source and add your classes as a module. Cuts out all the gdextension glue code and then you don't need to ship a shared library.
Note: We have a fork of godot that has some changes and fixes weve made and engine upgrades are still a breeze. Solving the odd merge conflict is not that hard, people do it all the time. Godot's code base isnt drastically changing from day to day. 3->4 only had significant impact if you were doing certain things with the 'visual server'... other than that even that was easy.
I now have at least 50 GDScript files and not a single C# file, the language is good (with types).
My only issue is that I can't get Copilot in their integrated IDE and that Rider's GDScript plugin doesn't support anonymous functions right now