Does this exist?? It sounds like it would be incredibly tasty! Coconut and mango are two of my favorite flavors, and I'd maybe do a keylime filling if that exists. I thought I'd ask before I started trying to create something on my own!!

http://www.cakecentral.com/cake_recipe-2663-Coconut-Mango-filling.html theres a coconut and mango filling im wanting to try, hope that gives you a start!
xx

1 box white cake mix
1 c flour
1 c sugar
1/2 t salt
1 pkg coconut pudding mix
2/3 c Mango nectar (Kerns
2/3 c coconut flavored coffee creamer
1 (6oz) container coconut yogurt
1 (6oz) container mango yogurt
3 eggs
2 T oil
1 t coconut flavoring
1/2 t LoRann mango flavor

Have you seen this thread?
http://cakecentral.com/modules.php?name=Forums&file=viewtopic&t=614554&postdays=0&postorder=asc&&start=0

Maybe do your favorite coconut cake and fill it with alternating layers of mango curd and your key lime filling?