How would the game know if your organs would work? As you have to design them yourself, how would the game decide, for example, how much force your tail/fin/superflagella (don't know the correct word) could convey?
I love how detailed the theory team has ideas for, but the real hype comes from the programming team. But it's the journey, not the destination when we have projects like these. I'm working with some other people on a Terraria texture pack, everything in handmade HD sprites. We only have ~1350/9000 (15%) of the textures done, and the game itself is growing. The original author came in, uploaded all his contributions, and then handed the reins to the other contributors. It was tearjerking, but the project is huge and we must move. Thrive is huge. We can and must proceed.