An oldie, but let me do some brainstorming.

1. If you are going to have thousands of clips, you definitely need to construct a rig, not only **for the models but also for the lights and cameras**.

    For the model make one structure to be adapted on a comfortable chair that gently directs the orientation of the head.

2. Prepare a digital projector to shot a grid or a **silhouette** from one side of the model **(be careful with the eyes)** as a reference image.

3. Or prepare a set of orthogonal cameras, that can Livestream to a computer. If you are using windows, there is a small program called "Ghost win Real transparent windows" that can overlay one application over the other, a reference image. These cameras need to be also attached to the rig.

4. You could use a flat background, so you can align the clips in post pro.

5. Combine all the above.