They actually do have that option with Pandora, as the only big fictional elements of the fauna are the trees that glow and the various giant plant life. Everything else is generic enough to count as some kind of tropical rain forest plant. Even the Discover Pandora feature that they did during pre-production calls most of their vegetation rain forest like pants. The only thing that would require actual construction in a controlled environment would be the glowing spirit tree at the least.
And I believe I also read an article saying that a large part of Pandora's location was inspired by a place in China.