We have discussed the possibility of adding the legacy ServiceMBeanSupport and associated classes over, but have not put forth the necessary work yet. We will put something in place to at least help bridge the gap with the 7.1 release.
What are you using from the base class? In most cases just removing the dependency on the base class works. We will call the correct methods as expected, we just don't have a base class to extend.
Ok. We do have an app that is suppose to start some services and in other application servers we do use the lifecycle mechanism. One way in AS5 was to use the ServiceMbeanSupport in order to kickstart that services.
If your application is a EJB app, then you can include a @javax.ejb.Startup @javax.ejb.Singleton bean which is triggered on application deployment. You can do any initialization stuff in the @PostConstruct method of that bean.