This should be done the other way round. All the properties that you want to have in your control, should be exposed in the control's class. Then, in the designer, you can set these properties, from the client-side script, by calling the this._propertyEditor.get_control() method that returns the control class with all of its properties and lets you set their values.
Here's an article that can explains in detail how to work with control designers:
Let me know if you need further help with this.