Intriguing!
That's basically how I go about plotting out stories, so it makes sense to me. I like the idea of combining the archetypes to get your character - it reminds me of those children's games where you have three sets of cards attached to one cardboard body and you mix and match the bottoms, middles and faces to get odd or interesting combinations.

I love JMS' storytelling ability. And yes, it's usually about: what will this person do if THIS happens to them? Why do they react that way? etc.