Finally you need to create your main custom organization service class. It must extend org.exoplatform.services.organization.BaseOrganizationService. BaseOrganizationService class contains organization service unit handlers as protected fields, so you can initialize them in accordance to your purposes. It also has org.exoplatform.services.organization.OrganizationService interface methods' implementations. This is the class you need to mention in the configuration file if you want to use your custom organization service.

You can find example of such class at subversion server: JCROrganizationServiceImpl.