an idea..

abstracted-app.dart

void main() {
  runApp(MainApp());
}
class MainApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    MiniApp miniApp = MiniApp();
    return StreamBuilder<Object>(
      stream: miniApp.stateStream,
      builder: (context, snapshot) {

        if(snapshot.connectionstate=waiting) return loader

        if(snapshot.data!="AUTHENTICATED")
        return miniApp.buildWidget;
        else
        return other;
      }
    );
  }
}



//let this be the mini-app

class MiniApp{
  Widget w;
  Stream s;

  MiniApp();

  Widget get buildWidget
  {
    return Builder(builder: (ctx){
      return MyApp(); //pass stream controller etc to widget and set s
    },);
  }

  Stream get stateStream
  {
    return s;
  }

}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return StreamProvider.value(
      child: MaterialApp(
          title: 'Flutter Demo',
          theme: ThemeData(
            fontFamily: 'PS',
            primarySwatch: Colors.red,
          ),
          home: Wrapper()),
      value: AuthService().user,
    );
  }
}