if you think the character might be overdone, but you still want to do it anyway, you could maybe try doing something that will make YOUR version of the costume unique? I also cosplay KH2 and 358/2days Riku. But when I do OrgXIII, I use an Oblivion (or carry a plush heartless depending on whether my keyblade's been banned from con)...and my normal KH2 Riku I have a way to dawn that's taller than my Roxas. >.>
Finding ways to make yourself different from the other people in the same costume is one of the fun parts of cosplay?
~*~ Member of Cannot Unsee ~*~