Krehfish,
I've been away from the island for too long - will be back early next month. I don't think I'm going to like the increased pace and scope of development. But, if development continues, I think you've got the right idea with development fees. I think a variant of California's Mello-Roos districts should be considered. In a Mello-Roos, the property owners within a district are responsible for payment of improvement bonds that are used for schools, parks and infrastructure.
New developments on AC not only alter the island's quality of life, they strain the existing infrastructure. Hopefully the Belize government will implement reasonable development controls before Ambergris Caye gets completely "Cancun-ized."