Can we remove dependencies on saxon extensions?

[Klortho]

The readme mentions that these depend on some saxon extensions:

As described in the documentation, these are XSLT 2.0 with Saxon extensions, and require a recent version of the Saxon processor to run. (Tested under Saxon 9.4.)

It would be nice if we could make them processor-independent, or, at least, only dependent on Saxon HE (extensions require either PE or EE).

If that's not possible, could we update the README to be more specific, that PE or EE is required?

P.S. This was reported by a potential user.