So what happens next? One approach is to finalized the envelope and then fit the components inside; another would be to arrange the components and then 'flow' the envelope around it. The former limits your choice of components, the latter requires you declare your variables.
The Template side view that kach22i has a front view as well. It's half-circular and flat on the bottom. The curved underbody you've shown is more similar to a Luigi Colani design based on the shape of a water strider.
It is flat on top and curved on the bottom to counteract the lift that the Template would produce. Another reason I prefer the Trophenwagen-type tail end.
When you get to the door cut-lines, my favorite four-door is a Ford concept, the Evos:
Mainly because the front butterfly doors hinge on arms to the windshield center.