I think there should be a version of RhinoApp.RunScript which doesn’t return until the script is completed, regardless of the execution context. The feature doesn’t seem very difficult to code, yet it will enable possibilities of complicated back-and-forth interactions between Rhino and external code.
For instance, there’s an ExportAs component in my GH plugin and it calls Export command from Rhino. As of now, I use RhinoApp.Wait & InCommand to determine if the script is over. The approach runs into problems from time to time. I believe it would be much nicer if Rhino SDK could tackle this.