Glad you had such a great time! Thanks for such a detailed report, too.
We have been with Divetech for both of our trips to GC and have really liked their style - we're taking some friends there next week, in fact, so I was glad to hear that Lee is still there (always enjoyed bantering with him!).
About the comment about someone being on the boat - I think every dive I have done has been like that - the boat was never empty, and I'm talking Cozumel, Curacao and Cayman (I guess I like diving the C'c ;-) I think it's a better idea - if someone surfaces early for am emergency it seems like it would be easier for them to get fast help, rather than one of the guides having to do an emergency accent and possibly have the same problems, no?