Northeastwrecks:
I agree that the requirements for going pro are ridiculously low. IMHO, the short answer is that you should become a dive professional, but not an instructor, when:
1. you have mastered each and every skill to the point where you can perform them at demonstration quality, i.e., flawlessly, while hovering;
2. you have the situational awareness and skills to control a group of new divers and the willingness to take charge of a situation and control it;
3. your rescue and watermanship skills are sufficient to handle a diver who has experienced an emergency, who is panicking and/or unconscious and who is completely dependent upon you to get them to the surface safely. You should also be able to handle the diver's buddy and surface the entire group safely.
4. You are thoroughly familiar with the conditions in which you will be teaching.
5. You are capable of performing basic field repairs on equipment.
6. You are comfortable and capable of conveying information to groups in an understandable way.
With regard to the dive skills, I don't see that it can happen in less than a few years. You need to be so comfortable with your equipment and technique that your reactions are instinctive and automatic. That way, you can concentrate on the people under your care.
IMHO, a few years as an active DM or AI should be necessary to become an instructor. In addition to everything above, you really need to see the things that students and new divers will do before you are qualified to take charge of them.
This is a great checklist, and I've been thinking about it for a few hours. Unfortunately, it's also really subjective, and I think it would be difficult for an individual to be able to appraise their performance in these criteria. For example, I would suspect that if you asked the current DMs and instructors, they'd all say they are completely qualified to be in the positions they are in, while their critics would argue that half of those instructors shouldn't even be in the water with scuba equipment.
While I like the idea that I have some "goal" based on this list (rather than just plodding along without any real clue what to do "next"), I almost think it should be the determination of another instructor, or an unbiased agency (like DAN, perhaps?) to determine who is ready to undertake leadership roles in scuba.
In order to prepare to meet the challenges of this short list, there is obviously a great deal of practice involved. Have you ever done practice dives, where you and your buddy dive specifically to work on skills (as a non-professional)? Do your buddies get annoyed that you want to spend 45 minutes doing nothing but removing your weight belt, and putting it back on again under water?
If there is one thing that has stood out in the training that I have received so far, it is that the courses offered by certification agencies do not prepare you for very much. I have learned more by reading from web sites and these message boards than SSI would ever teach in their entire collection of manuals (most of which read like brochures for other classes). If someone wants to LEARN diving...what are some alternatives? In other words, I don't feel that I will benefit from reading the basic open water manual 30 times, because it's all very simplified, and leaves many more questions than it provides answers. Instructors should be able to field questions that arise from students, but where the heck do instructors gain additional knowledge, if not from courses? "Experience" can be a great teacher, but most of what I'm looking for is also sheer academics -- the academic side of scuba is very nearly as intruiging to me as the actual diving.
I'm rambling...so it's time to shut up.
-Andrew