I'm definitely with xianfeng on this one... Diddy Kong is one of the characters on the top of my list (the only characters I want more would be Marth returning [if that counts], Samurai Goroh, and Krystal in that order). He's been the type of characters who's really major and yet hasn't been placed into a Smash Bros. title (think back to the demand for Wario, and now... voila!)
You've supplied an excellent moveset, covering every last detail from speed and range down to a victory theme song. If Nintendo is reading this thread, they will definitely put Diddy in without a second guess.
My estimation of Diddy's chances of making the cut: 85-90%