Actually, the two are orthogonal. You can monkey-patch an aggregation into a model as easily as you can monkey-patch anything else in.

Also, modules aren't monkey-patching. :)

  http://en.wikipedia.org/wiki/Monkey_patch

Lastly, the modules referred to in the article were added statically, not dynamically. We don't use a lot of dynamic module inclusion (though we do it some).