Well, here's the main thing you guys should think about...say he really wants to give the DK series more rep, and he's low on time or something (I really don't think that's true, btw). But, let's say that for whatever reason he isn't able to give DK more rep than just Diddy and he wants to. Could he possibly team him with Dixie just to give him three reps?
Personally, not that I care for the character, but K. Rool adds to the villains list, and he helps DK more of like a hero than just some big hairy ape who used to steal princesses away from Mario, aka "jumpman"...Anyway, you think this would be a reason that Sakurai might do the duo??