Alright, I've been following this sub-reddit for far too long without saying anything, but your post finally made enough of an impact that I thought I'd contribute. "To bad we aren't farther along..." suddenly made me realize that we really haven't left the starting gate, despite being a sub-reddit for 2 years. And it seems like you, Citizenpolitician, have an active interest, so let's talk.

Here's what I see as the fundamental causes of our inertia. Feel free to disagree or add your own. Only by solving these does this project have a chance of moving forward.

1. If the project ever came to fruition, it would mean that a certain number of people would need to live there full time as executives/managers/caretakes. Until we have an active list of people willing to stand up and say "I will give up my life as I know it to move to an island and turn it into a community", this project is nothing more than a pipe-dream. It's going to be difficult to find people willing to give up their jobs and move to an island for an untested project. We need to identify those people.
2. What is the scope of this project? Above you talk about sustaining 35,000 to 50,000 people. That seems like a difficult proposition. We need to determine what the community goals are. Are we looking for a full time community of 10 people with the ability to accomodate another 50 guests / tourists? Are we looking at a 100 person community or a 1000 person community? Knowing the population requirements will help guide the reaction we need to my above question #1.
3. The island itself. If we can determine #1 and #2, we can significantly narrow down our island options. I think we'll have more luck organizing funding if we have a specific goal in mind, rather than 10-20 vague ideas about raising money for such-n-such island. It's far easier to say "we need to raise $2.3 million to buy X island" and get results.
4. True organizaiton. Once we determine #1-3, we'll need to organize in a legal sense. That will help with fund raising and further scoping of the project. Eventually, we need to determine the details of what will be built, the cost of running per year, tourism implications, etc. I'm not a lawyer and have no idea what the ideal organization would be. It's probably dependent upon what the answers to the first 3 questions are.

Now, I'm not personally ready to lead any project just yet, nor am I willing to give up my life and transport myself to an island and play hippie/tourguide. I just know that we'll continue to be a floundering community unless someone steps up and helps answer the fundamental questions. I'm ready to help, but not ready to lead. :-/ I wonder if that's the achilles heal of the whole thing.