This seems to work as expected, except when creating a widget type one has to duplicate the inputs sets to GetDefaultSettings( & $params )

in other words if one only define the params in get_widget_param_definitions( $params ) then it doesn't 'register'. In order to work in Widgets on has to create 'skeleton definitions in ' GetDefaultSettings (See below)

Is this not redundant?

function GetDefaultSettings( & $params )
	{
		global $app_version;
		return array(
			'plugin_sets' => array(
				'label' => T_('Label Name'),
				'note' => T_(''),
				'type' => version_compare( $app_version, '6.6.5', '>' ) ? 'array:array:string' : 'array',
			'entries' => array(), // No need to add the params here, BUT IT MUST BE DEFINED FOR WIDGETS
		)
			);
	}