I am curious if it's possible for QMC2 and even baseline MAME to support custom made XML files as an alternative to using category ini files or Arcade only derivative builds.

Here's a quick and dirty MAME.xml

The idea would be to either import or point QMC2/MAME to this XML file and an entry name MAME appears in the Machine listing (Since example involves MAME.xml) as a method to generate a custom listing.

Obviously I would need to add the appropriate info. at the top of the XML so name and description is known.