So I built LibXLST for all platforms (2x Mac, 4x iOS, 3x Linux and 2x Windows!) for me. Once the libraries can be linked to the plugin, I started make a new function for the MBS FileMaker Plugin: XML.ApplyStylesheet.
It allows you to apply a style sheet to an XML document and transform the XML to something new. Fore example you transform from one XML to other. This includes transforming XML to just text or html text. We'll certainly include a few examples with next plugins.
If you have ideas for more functions, please let me know.
By the way XSLT 2.0 is a common wish, but the problem is that there aren't many libraries for C/C++ doing that. And for example the Saxon library is quite expensive for redistribution.
Xojo has such a function built-in: XMLDocument.Transform, so no need currently for a plugin there.