Process Engine Plugin that only starts after engine has compltely started up including all secondary services?

postProcessEngineBuild fires before the engine has completely started up.

Is there listeners for things like waiting till the server has completely started up? such as waiting till the message ...org.apache.catalina.startup.Catalina.start Server startup in 1000 ms ?

There is no such callback. You would rather have to hook into the application server’s lifecycle, i.e. Tomcat here. Not sure what the exact procedure to do this is.