There seems to be a belief that c cards are just an "entry pass" with no real value behind them. Yet you go on to say "benefits that a course of this type, taught by a good instructor, might offer someone." Its not simply about getting the c-card (as a number of people on this forum seem to think it is). Dale, its exactly what you say. Its about "real benefits that a course of this type, taught by a good instructor, might offer someone."
The problem here is that the certification is trying to meet two different needs and groups of people. The needs of divers and the needs of operators. Divers don't need a card or a course to dive solo. Probably a good idea to understand the additional risks you are taking on and do what you can to mitigate them but a solo course isn't going to teach you anything you can't learn in any number of advanced dive courses. The ability to self rescue and plan a dive.
IMHO the course is all about the operators needs. Am I OK to risk my livelihood by allowing this diver to violate the "standards" of the industry. Some operators will make this call based on reviewing the divers experience level, a check out dive or gut feel. Others will require a certification. Certification is how most do it at the entry level i.e. you can't dive without a cert card, extending it to solo diving just makes sense.
If what you are doing is trying to meet the certification requirements of operators then you have a problem as you will have two completely different groups of divers that will want to get certified.
Those with significant experience - they need a course that is a glorified check out dive. A certification that says a qualified instructer has evaluated the skills, mind set and experience of this diver and they are qualified to dive solo.
Then you have another group that want to solo dive, but lack the skills, mind set and or experience to solo dive. They need a completely different course.
The first group of divers will not be interested in taking a course that meets the needs of the second group, and a course that meets the needs of the first group will not be sufficient to meet the needs of the second group.
I think the problem is a course that proports to be for the second group AND at the end of the course gives you a certification that is really for the first group. Hard to imagine a course that would take you from the second group to the first an a one or two dive course.
IMHO this is the source of the arguement I have been reading.
I have only taken one of the courses and it met my needs perfectly. It was a couple of checkout dives and a discussion about dive planning. I can't say I learned anything particular other than it forced me to deal with a number of unexpected situations, practice dealing with entanglement, deploying my pony and surfacing from depth using it. Hard to practice unexpected situation on your own, and crazy to practice getting yourself wound up with kelp or line. So all in all a good course for even an experienced diver. At the end I got a card that I have used several times on liveaboards to allow me to dive solo. In no way did it teach me the skills required to be a solo diver.
IMHO this course is all about operators liability. If you get more than that and learn or get to practice some self rescue skills, that is a bonus. Any thought that this course is going to take an diver without the necessary skills and mind set to dive solo safely and turn them into a safe solo diver is just not realistic.