The ball gripper pod design went fast at first, but bogged down when run against the design goals. . . positive mechanical lockout and sensors turned out to be a very big challenge. I am not satisfied relying on only electronic safeguards. In my view that is like substituting a proximity warning for a belt guard. Electronics can fail too easily.
After a couple of hours looking at three different methods, one of which is in the photos, everything finally came together with the ball gripper method. I figured out a bulletproof mechanical lockout and a sensor location and the thing is still buildable for less than a million dollars .

I shall put a Scottish flag on the finished product.
This project is headed for a significant pause because I am ordering material to make a batch of the new 4th axis next week. When that arrives, I won't have time to play. The BT30 spindle is also sold and ironically, I will be making an identical spindle as I was able to resolve the turret issue. I agreed to the sale so I'm going to honor that, of course, but it will be a setback, schedule wise, to make another spindle for this project.
If I can get a new gripper equipped pod made (NOTHING from the previous prototype pod is useable now), I will post it here. I would like to get one finished so that I can do the proof concept stuff at least, but we'll see how it goes.
Thanks once again for all of the comments and ideas.