It’s been a while since I posted an update on this project. Life gets in the way sometimes, but I’m back at it now.
The previous design enclosure that fits under the camera has been abandoned mainly because it makes holding the camera a little awkward. Especially when using some longer lenses when I need my left hand to grasp the lens itself the AF Assistant would not only get blocked (by my hand) but also make holding the lens a little weird.

I’ve talked this over with a few people and decided to move away from the bottom mounted enclosure.
The next design iteration will still be powered by 2 x AA batteries (I had considered using a 1 cell or 2 cell LiPo battery, but gave up on that as it complicates the design needlessly).  The enclosure will sit on the camera’s hotshoe and provide a pass-through to the hotshoe so you can still attach a wireless flash trigger or a flash, or anything else you may want.
Pretty much all the design is changed from the last iteration. The enclosure is new, the electronics will be different, and it mounts differently then the previous design.

Here are some screen captures of the design. The reference camera is a 5D Mk II.

For the AF assisting part, I will likely have 2 options available (at least for now). One using a laser and one using a near IR emitter.
More on this in another post.