DO you mean things like the port numbers
Tomcat will be using?
I have fuzzy indications that MAYBE server.xml can handle variable substitution, but ultimately server.xml IS a properties file. When running multiple Tomcat instances, you would normally split the CATALINA_HOME and CATALINA_BASE directories apart and keep a distinct server.xml in the CATALINA_BASE of each defined Tomcat.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.