How do you imagine sketching process? Is it tool, that supports touchscreen pencil? The problem with touchscreen pencil, that most people are not running ArchiCAD on touchscreen computers. Maybe that will change and most of the computers in the world will be touchscreen.
The power of grease tool in Blender, that it gives possibility to mix 2D traditional animation with 3D model.
I always was using simple lines, fills and text to sketch my mark-ups. There is also hand drawn spline tool available - that follows movement of the mouse.
If talk about sketching in 3D - you can use morph for that - it quite flexible to sketching in 3D.