For the sake of discussion, I would like to give my full stance on Bandanna Dee.
To quote the article on SG about
characters:
"To be blunt, if I think I can do it then I can envision a concrete embodiment of the character, but if I cannot do that the character cannot be made.” This is a big factor. Of course getting permission and understanding from the original creators is necessary, but
whether the image of the character in my head is dancing powerfully, or not. This is of the utmost importance."
I have been trying to think this way with Bandanna Dee, and honestly, I do not have strong feelings about Dee's moveset when I envision in Smash gameplay conceptual terms. Dee's move-set is simply not as sparking of an idea as Bayonetta's witch powers or Inklings using of ink. Even if he does fill in an interesting gameplay archetype, when I think of his move-set and his characterization in the Kirby games, it does not spark the immediate imagination. It is just there.
Would Bandanna Dee really be something Sakurai would definitely be strongly intrigued by conceptually, assuming that he lets the Kirby bias aside and actually prioritize this character over other newcomers? I do not think so. I feel there are other characters like Elma, Lycanroc, and Isabelle that would spark more interest, priority, and imagination to Sakurai than Dee. It could be argued that Sakurai could do creative liberties if the spear moveset does not spark some immediate moveset interest, but I feel that would be the case if Sakurai finds an important need to add another Kirby character for representation purposes. And in terms of Kirby representation, I think Sakurai is content enough with Dedede and Meta-Knight to not consider a 4th Kirby character for Smash Switch development. If there were a 4th Kirby character to be considered, I think characters like Marx and even Prince Fluff would spark more interesting moveset ideas for Sakurai than Bandanna Dee.
And I do take character archetype and moveset options into consideration. It is just when I look at Dee and compare him to other spear users like Azura from Fire Emblem Fates that utilize spears and have additional things going for her like being a dancing spear user, I would rather have the latter. How Dee utilizes the spear in combat is fine, but there is not distinct characterization in how he uses it that would make him very attracting of a fighter. Almost every Kirby character utilizes their archetypal/elemental power in a cool way, but Dee doe not use it a way that has distinct personality to it.
Meta-Knight has characterization of him being quick fast-sword user in Kirby whose personality is mysterious and is a daunting ant-hero to Kirby. King Dedede is a heavy hammer user with a mischievous, greedy demeanor. Bandanna Dee personality wise parallels and acts a lot like Kirby that uses a spear, and does not have much to contrast himself beyond the weapon. Then what I am left with is just a potential newcomer who could fill in a spear archetype and utilize those weapons in a cool fashion, but provide nothing additional beyond that.
I guess in general, personality and the given moveset in RtD not easy to dance around with several gameplay ideas is why I think Bandanna Dee is not substantially unique enough of as a fighter and why I do not think he will be in Smash.