Add an alter hook for component defaults

Would it be possible to add an alter hook for component defaults? The use case is where a developer wants to effectively add additional functionality to an existing component type. Currently I've found that that's not tricky to do by implementing hook_form_webform_component_edit_form_alter() and adding additional fields, with '#parents' => array('extra', 'property_name'). I can then use this additional stored data within preprocess functions, form_alters, etc.

Obviously, defaults can be implemented with a simple isset() conditional. The problem is that some associated modules use the defined list of defaults for additional functionality. Specifically, Webform Localisation runs webform_component_invoke($component['type'], 'defaults') in order to generate a list of synchronisable properties. As is there's no way I can make my added properties synchronisable without hacking Webform Localisation.

I've attached a patch which adds an alter hook. I appreciate that this doesn't actually resolve the Webform Localisation issue, but it would set up a standardised interface hook that modules like Webform Localisation could invoke, and add extra benefits, such as being able to override defaults to those most appropriate to a specific site, which would help admins in instances where they would otherwise have to change the same value in every new component added.

I have raised a corresponding issue on Webform Localisation's issue queue (Allow list of synchronisable properties to be altered)