The issue I see with XSLT is it’s yet another technology to learn. The beauty of MODx however, is that a plugin or module could be written by anyone to take advantage of it. So while it won’t be a core "out of the box" component, there’s no stopping anyone from tackling the job.
Did you just volunteer?!?!
Ryan Thrash, MODX Co-Founder Follow me on Twitter at @rthrash or catch my occasional unofficial thoughts at thrash.me