Every 3D Cad designers can design a part of the chassis of a notebook, there are CAD 3D in cloud to collaborate or we can work on the same open source repository.

Open Source 3D Cad

FreeCad

if you know others please tell us.

We have found these

Cloud 3D cad

http://clara.io/

https://www.onshape.com/

if you know others please tell us.

Laptop Open Source 3D Cad

We have scaled the original OpenSource Via OpenBook chassis to around 15.6 inch,

that could be a starting point of development , here our repo

https://gitlab.com/oshw-powerpc-notebook/open-laptop-chassis