An idea about how Y.Dialog could be made

gistfile1.js

Y.Dialog = Y.Base.create('dialog', Y.Widget, [/* same extensions as Panel */, Y.WidgetForm], {
  initializer: function (config) {
    // deal with inyecting a View inside the body of WidgetStdMod
    // config.data could have the initial data for the form
  }
});

var dialog = new Y.Dialog({
  template: someTemplate,
  data: someData
}).render();
// dialog.form is an instance of Model
// (I'm still not very familiar with the app framework, so this is a rough idea)
dialog.form.get('foo'); // returns the value of the 'foo' input
dialog.form.toJSON(); // models get this one for free