Although FreqX is much faster than it used to be, it could probably be faster.

Using fn:transform() might let multiple XML catalog files be used. If not, the author has written an XSLT-based DTD parser that could possibly be integrated and used (at the expense of speed) where needed. It is not, at the time of writing this paper, possibly to supply a catalog resolver to the XPath fn:doc() function, unfortunately. FreqX does, however support combining results from a previous run with a different XML catalogue file in use, which can mitigate this problem.

Additional output formats and additional visualizations may be helpful. A JSON report is in the works, along with a treemap visualization based on d3.js.