I don't know much about CAD requirements, but it looks like there are a few tools available already and efforts underway:
The CAD addons for blender are helpful for doing some more precise drawing actions (like finding the intersection point of two edges, which blender doesn't normally give you), but they're still fundamentally in a destructive mesh workflow. You have a pile of vertices/edges/faces, you do some editing, and you have a different pile of verticies/edges/faces. There's some stuff doable with non-destructive modifiers, but they're for very limited specific tasks.