Historical Open-World Map Creation

Hello, I would like to have an Unreal Engine 5 map designed. It would be a jungle island (think sort of caribbean inspired) covered mostly in jungle type terrain, a few rivers winding through it, with a mountain range and volcano in one area, as well as the surrounding sea floor. I would like it to follow earth like geography as much as reasonable. I would also like it to be able to be dynamic, with native villages potentially moving around, maybe little charcoal/fishing/hunting/lumber camp type villages dotting the landscape, and the ability to be developed by an exploration group (building port cities, establishing mines, etc.) I'm thinking I would like it to take about an hour to traverse from one end to the other on foot at it's longest point (to encourage travel by sea), as well as being longer than it is wide. I would like it sparsely populated with existing native villages, maybe a couple hunter's camps or exploration camps, as well as a few port cities spread around the edge of the island. Most importantly I would like collaboration with you during this project to ensure proper understanding of goals and design philosophies. Other than that I welcome creative freedom. Is this something you could do? What would your timeline and cost be for something like this? Thank you for your time and consideration.