Quote - I wonder if something closer to Unix-like file paths with wildcards would be useful.

Actually the concept(s) your looking for are provided by XPath.
As Poser files are structured and hierarchical information which quite naturally map to a set of objects in a tree structure exactly like the XML DOM.
There's also at least two free libraries that implement it for you
-> http://commons.apache.org/jxpath/
-> http://jaxen.codehaus.org/
The JXPath library is probably the better of the two as jaxen needs you to implement interfaces for custom object models rather than working "out of the box".

Given the similarity of Poser files and XML files, having a DOM-like model and/or adaptor would allow the use of XSLT to manipulate them.