Literally every time I see somebody bring up an idea, all I hear is "He can use a spear". That tells me nothing. You can use a spear to stab just like a sword, and Bandana Dee's body type doesn't really lend itself to taking advantage of the range a spear can give you, in my humble opinion.
A moveset that makes itself =/= a fun and interesting one. If all he does is stab and throw spears, it doesn't sound all that exciting. Now, if an actual playstyle were proposed, such as a zoning character (because of throwing spears), then we're actually discussing something that could be interesting. (Also, as @
N3ON
said, I really do think people are overstating his importance to Kirby, and I myself don't see why he should be included over a lot of other choices).
As I've said in general before, if Bandana Dee gets revealed and looks cool, then I'd be convinced. But the ideas I've seen so far don't paint an interesting enough picture, at least for me. The idea is to convince everybody "Hey, you're really gonna want to play as this character". So far, every character has pretty much struck that chord with people. The only one MIGHT be Palutena, and even then we haven't seen her actually in gameplay. The movesets I've seen for Bandana Dee don't really get me excited, but then again, none of us are Sakurai here. I don't expect people to be either.