Logic that attempts to do this "by hand" becomes extremely specific to the XML data structure that was originally parsed when it was originally written, and can be extremely difficult to accurately update when the XML definition changes.

This sentence could just as well apply to XSLT. Properly written Perl code will be easy to adapt to changes in the XML.

Fully-leveraging XML technologies via these standard binaries eliminates great code complexity

I've written XSLT, and I found its syntax somewhat cumbersome.

Plus, Perl is much more powerful (regexes, the ability to access other data sources like databases, JSON, and so on). Sorry, I currently don't see the strength of your argument for XSLT. But perhaps you could write an XSLT solution that demonstrates its advantages.