Ok, so I confirmed the obvious. We made the decision early on to keep the models and rig files separate.
Modelers work on the models, UV materials and so on. The structure inside the file is always the same.
The riggers append and update as necessary the updated model into the rig file.
They work closely with the modelers on this.
Modelers provide a proxy model until all retopo is done and often animators use the proxy model even when the final is finished for rendering.
So the file linked into the layout scenes and animation scenes is this rig file.
For materials, I outlined the workflow here: