pipedope:The problem is that there is a whole spectrum of diving ranging from the guided tour to the saturation commercial dive. In the mid range is technical diving.
Technical diving (the term) was invented to relieve recreational agencies of liability and relieve divers from commercial rules so they can operate in the 'gray area'.
Commercial diving is very technical not just because of the equipment and dive profiles but because of the planning required and most important because of the focus. Commercial divers are not there to be 'diving', we are there to solve a problem or do a job and the dive is just how we get to the work site. We have to be able to concentrate on the JOB and not think much about the dive while we are working. This means that all of the diving skills and emergency handling be automatic.
I am a strong supporter of individual choice but if you are thinking of doing a commercial dive job (and are not a commercial diver), ask yourself why is someone willing to pay me to do this? Do I really know ALL of the significant risks? If things go wrong, will I survive? and will my insurance pay?
When it comes to pipes, dams, and salvage of anything bigger than what you can personally pick up then unless you 'really' know what you are doing it is better to let the pros do it.
The typical commercial dive school takes 3 to six months of 5 or 6 days a week just to get you to entry level skills and knowledge`.
In short, Tech Diving is anything in the gap between recreational diving as defined by the recreational agencies and commercial diving as defined by OSHA/USCG or other organization in charge of working dive regulation in your region.
I don't think that technical diving is between recreational and commercial diving at all.
In reality very little of what a diver learns in typical recreational training is of any value at all in technical diving beyond simple things like clearing water from a reg or something.
Much of commercial diving is completely different that recreational or technical diving. As you know, much of the equipment is completely different and so are procedures.
However, while a technical diver may not be a welder, plumber or be equiped to handle many of the jobs that commercial divers are trained and equiped to handle, much of technical diving is mission oriented. When the dive has a mission, as you say, the diving is just a way to get to the site. Much of technical training concerns mission planning.
I guess the thing I'm getting at is I don't think we can describe diving on a scale from recreational to commercial since the only thing the three really have in common is the water. In each case the skills and equipment are largely exclusive.