Hi Martin - I was worried about this case as well when we were working on the Ajax/ClientBehavior APIs. Many Trinidad/ADF Faces components use similar markup to what you describe.
To support this case, we added the ClientBehaviorContext.getSourceId() API: http://download.oracle.com/javaee/6/api/javax/faces/component/behavior/ClientBehaviorContext.html#getSourceId() This allows renderers that attach client behaviors to non-root DOM elements to explicitly specify the id that corresponds to the component. This value will (or, well, should) be passed in as the first argument to jsf.ajax.request() and used as the replacement for "@this" targets. Andy
