It's certainly possible, especially if a patch is supplied.
However, if you have a custom stylesheet that accomplishes what you want, it'd be nice if you could provide a patch for pmd.jsl, so that other users can profit from it, too!

The attached stylesheet includes a breakdown of priority totals for the project and for each file. It also sorts the errors for each file by priority and lists the priority against each error. See http://pcgen.sourceforge.net/autobuilds/pmd-report.html for the output on a large project.