Incorporate Saxon - primary motivation is for XPath 2.0 support. Other benefits too
do you plan to Incorporate Saxon 9.x (e.g. Saxon-HE 9.7) ? Saxon 9.x now supports XQuery 3.1 / XPath 3.1 which is very nice stuff.
As you can tell @kpopovic , this issue is relatively old , but incorporating Saxon support for >XPath1 support is still a "good idea". I originally worked with the Saxon folk a couple of years back to get better integration. It's a little challenging. I think though, that the time is right to revisit some of that work.
Note that the vast quantity of return-types from >= XPath2 is a headache from the API perspective. The Filters concept in JDOM addresses some of this.
Bottom line is that I am not actively integrating with Saxon right now, but I will have a look and see if there are any horrible implications of doing it.