Jeremy, resorts and dive ops are also travel professionals--it's not just agents. When you use one source for all of your bookings, things go a lot more smoothly. I can tell you truthfully that I've had a few US-based liveaboard customers who, because they're used to direct bookings in that part of the world, went ahead and did what you're thinking, and then got into difficulty once they were here and had nobody to turn to to sort things out for them in a place where they don't know how things work and don't speak the language. When they subsequently called me for help, my hands were tied since I had nothing to do with the secondary bookings. The more links in your chain, the more potential failure points, and if you need contacts for each one of them because of individual bookings you've made directly, imagine the mess if you have a flight delay and can't tell the driver or hotel or dive op about it without making a ton of calls and trying to talk to random low-level staff who have not been involved in your bookings. It's just friendly advice from somebody who knows....
As you can see from my badge, I'm a SB Staff member, and I am all about encouraging people to share their experiences and expertise here, and you're right that our members have a wealth of experience, but I really believe you'll get better results for yourself and your trip if you get professional advice first and then confirm your short list of ideas here with people who have actually stayed at resort X or dived with operator Y.