It's important to keep in mind that as OmniFocus is currently implemented, there are no subprojects. Repeat:
there are no subprojects. There are folders, projects, and action groups. An action group is a way to organize related actions, but it does not appear in context mode (unlike actions) and does not have project features such as independent status (active, stalled, on hold, dropped) or review times.
You may think this is a silly way to implement something between an action and a project; you may prefer something like Life Balance's implementation. But until the Omni Group changes action groups (if they do), it's important--for your peace of mind if nothing else--not to think of them as something they are not. See
http://forums.omnigroup.com/showpost...07&postcount=5.