AE already has extruded 3D. Just use a shatter effect and don't shatter it. It is true that you do not get bevel and texturing is limited, but you can get a 'true' 3d extrusion out of AE.
Yes, I have seen this in use. And you're right, even though I would characterize this as yet another workaround to achieve something that AE isn't 'made to do'.
Yes, it is a better workflow to remain inside a single app.
I guess, having worked in 3D and 2D I see the setup and maintenance of this footage techniquie to be quite a burden. If a texture change is requested, instead of a camera change you are still in the same boat of having to go back to the 3D app and re-render your footage.
You're right. You are locked to one light setting (except AE's light onto the footage 'plane', which wouldn't change the 'real' lighting on the object), one texture and such... The only advantage I guess is to be able to place an object in AE's 3D world and rotate it with 'pseudo 3D look' (?).
If you settle for one lighting and one texture, you have a 'full 3D look' which needs no more adjustment.
Thanks for your feedback. I really appreciate it. Feel free to comment more on this.