This would be amazing! I would suggest starting to shoot for Baily's Beads about 20-25 sec before and about 15 sec after C2. Reversed order for C3. For totality, shooting a bracket of 11 or 13 stops would be good as well. A bracket step of 1 EV should work well. Smaller EV steps shouldn't be needed ...

Nice writeup. I have an A7III. I'll try your testing and see how it goes on mine.