Trivial. I love and hate that programmer's word. But it seems the appropriate one to use here.
I thought that since XSL FO can be used to transform XML into PDF, then surely there must be a way to easily tranform into RTF without getting into directly creating RTF. No such luck. Hell, doing FO PDF transformations doesn't seem too easy either. Problem is that FO processors are in their infancy. The processor that we would probably consider is FOP for Apache. But this still only gets you PDF.
I'm still looking for a method to transform XML to RTF non-trivially. Will come back with anything I find.