I like that way of saying it — you’re doing a little upfront thinking, to make all subsequent decisions require less.
I’m thinking of doing a how-to for implementing this. Just have to test it out and make sure it works.
Your comment on tasks that belong to areas, but not projects, starts to get into task management, which is a whole different ballgame. PARA extends from GTD, but is very specifically for non-actionable info, to avoid the dilemma you describe of tasks not assigned to projects getting lost. “Losing” something in an area folder need to be not a big deal.
Why do you think it requires tags? I’m actually quite against using tags for long-term purposes. Omnifocus again is for task management, not personal knowledge management. Maybe I should make that more clear.