Though I am not 100% sure if this solution will work, I know that you can change the .ftl files in your hibernate tools jar file to make changes to the way the java class files are generated. I had used it for making changes to the cascade property being applied to the relationships.
You can check my thread for manipulating the cascade attribute here
https://forum.hibernate.org/viewtopic.php?f=6&t=985004Hibernate-tools.jar/pojo/Ejb3PropertyGetAnnotation.ftl should be a fine place to start looking at.
HTH