Diddy was singled out as a unique, important and popular Nintendo character (the latter of which the DK64 Kongs are not) to add into Brawl, not as a "DK Rep." Sakurai may have
planned Dedede in 64 and as two separate back-up options in Melee modestly held off on Dedede due to him being from Kirby, but he didn't consider Dedede in the first place or add him into Brawl for being a "Kirby Rep."
You're claiming that the team does double the ordinary amount of work, arbitrarily penciling in "Reps" for every bit of series content in the game, then going back over a second time and deciding on the specific content, seemingly just to justify the use of a fan-made term. Not only is there no evidence to support that, it's just not practical when the team can just decide on content on its own merits, loosely balanced out by series' relative importance/popularity.
. . . . .
Anyhow, I'll be making a response video addressing the entire thread once we find out the final roster, one way or another, but until then, one last time. . .
Long live the king!