emberjs: add routes after app initialize() - ember.js

Question

i run into the following problem when building a router based app with emberjs. My app is simplified structured as following:
var App = Em.Application.create({});
App.ApplicationController = Em.Controller.extend({});
App.ApplicationView = Em.View.extend({
template : Em.Handlebars.compile('APPLICATION TEMPLATE')
});
App.RootState = Em.Route.extend({
index : Em.Route.extend({
route : "/"
})
})
App.Router = Em.Router.extend({
root : App.RootState
});
// initialize the app here
App.initialize();
// extend the RootState from anywhere. eg. from a plugged widget
App.RootState.reopen({
login : Em.Route.extend({
route : "/state1"
})
});
//App.initialize(); //init the app a second time forces unexpected behaviour
App.RootState.reopen({
alarms : Em.Route.extend({
route : "/state2"
})
});
//App.initialize();
Like my app demonstrates, i try to extend the router with new routes at runtime. I know that there exists another thread with similar question exists, but the discussed example do not work for me.
How can i extend my router at runtime with additional routes, without calling initialize() after every ...reopen({ }).
The background for doing this is to decide at runtime how the application is look like, for example to plug in different wigets with their own routes.
Regards,
T