We have a hard time for creating a custom plugin for a dialog pathfield.
The official documentation : CQ5 | Widgets API says that we can add plugins on pathfield
plugins : Object/Array
An object or array of objects that will provide custom functionality for this component. The only requirement for a valid plugin is that it contain an init method that accepts a reference of type CQ.Ext.Component. When a component is created, if any plugins are available, the component will call the init method on each plugin, passing a reference to itself. Each plugin can then call methods or respond to events on the component as needed to provide its functionality.