since the implementation of EZP-24129, shell.html.twig receives the full application under a parameters variables. This variable should be directly injected to application. Basically, we should get something like:

            var app = new Y.eZ.PlatformUIApp({
                    container: '.ez-platformui-app',
                    viewContainer: '.ez-view-container',
                    config: {{ parameters|json_encode|raw }},
           });

Then in initializer, the config should be dispatched to the existing attributes. The attributes filled this way should probably be set as readOnly as well.

Of course, that means some tests will have to be fixed and added as the logic implemented in shell.html.twig was not tested.