Lots of good ideas so far.
Getting flashbacks of ratpacks and fieldcraft manuals, can't believe I actually have fond memories of rat passions. Although I have often thought that hexamine stoves are designed to smell bad to soften the impact of the taste of the rations.
I guess what I would have in mind would be (as suggested);
*Getting a group together (8 to 10 sounds about right)
*Choosing a suitable location with the right balance of support and adventure
*Finding a local guide(s) to make arrangements 'in country'
* transport/accomodation in the form of jeep/tent or small liveaboard. depending on Terrain/access could consider a RhIB
* Duration (hmm would like to say month plus but maybe should start at 2 weeks)
The main decision has to be location, which bring up the following points;
* distance v cost - to go somewhere relatively uncharted we would need to go somewhere quite remote. although North Africa sounds promising as a compromise. Having said that for a first time, even some of the less dived areas of Europe become a possibility. I don't know how people would feel about doing this in Egypt for example, and trying to do Sinai, Israel, Jordan and Saudi (Saudi of course being a nightmare for bureaucracy and passing through Israel may stop entry into some Isalmic countries), or going the other way to Sudan. Maybe you could do a lap of the Red Sea
.
* Access to services, diving and emergency. Diving - Ideal would be compressor and enough spares to keep people diving. Emergency - this is where the local guide really comes in, but careful planning (first aid, O2, training and comms) and setting the skill level appropriately would also help, e.g. min Rescue (i.e. PADI RD or BSAC SD), current first aid, 50 + dives and some Leadership/expedition experience/taining in the group (although the latter could be the guide).
The starting points would be;
1. Get a Party together (min 4 max 10 with some commitment)
2. Choose a location (Still open to suggestions)
3. Identify and contact local support
4. Plan plan plan
Until 1 and 2 are sorted the rest is redundant.
So anyone interested in planning an adventure then shout and start throwing some ideas in the hat.
You never know, if we find a new reef it could be named after YD