With JIRA 7 + Tomcat 8, the JSP are now pre-compiled in atlassian-jira\WEB-INF\classes\jsp and no more compile on start up in <tomcat-install>\work\Catalina\localhost_\org\apache\jsp

If there is no more way to extend JIRA by copying new JSP files or modifying existing JSP, then all features based on that has to be redevelopped !!!