In AbstractWarDeployer there's some code that unpacks jars into the tmp directory. This looks to be some limitation related to Tomcat not using the VFS from the comment
/* Unpack wars to the tmp directory for now until tomcat can use the vfs directly. Since
* the vfs deals with the distinction between a true directory, the only way we can tell from
* this level of the api is to look for a url that ends in '/'. Here we assume that the name is
* the root url.
If we're going to do this properly, then the tmp directory files should be replacing the VFS urls in the classpath of the deployment.
However, I bet Tomcat has some abstraction that we can override to tell it to use the VFS to load static resources?