Revo: Access to $modx obj via ajax-called class?

I know there was a similar topic posted on this subject suggesting the creation of a resource within modx that the ajax call would point to, which would subsequently run the necessary logic via a snippet. I get how that works. I’m curious if there’s a more elegant way of doing this, not requiring a new (and volatile [i.e., unknowing client admins/editors could easily delete it]) resource. Is there a good method for picking up the current object or easily creating a new instance? In evo there was a method by which you’d create a new class/api extending the original document parser (i.e., Raymond Erving’s MODxAPI). I realize this is ultimately more a php/oop (lack of mastery on my own part) issue rather than a modx-specific one, but any advice would be appreciated

FYI: I found what I was looking for in one of BobRay’s posts (http://modxcms.com/forums/index.php/topic,51895.msg301495.html#msg301495). Any downsides to creating a new instance of the modX class?