TWO dramatic introductions, an actual backstory that will be relevant to the rest of the arc and create conflict and story points with the arc we're in, a connection to Ace, a unique weapon and fighting style, a quirk of a woman claiming to be a man? These are all actually unique things to the character. Child of an Emporer is unique to Kaidou, but BM has a million kids including Pudding, so its not that big a deal.
But the Oden worship is kind of like fifty other characters like all the scabbards. Dream seems very tied to the current location, and like they're just sort of here to help conveniently tie up some plot threads by coincidentally owning Oden's journal… and who knows what quick fix plot wraps ups that could provide later. Ace connection was already a thing with Jinbe, and Tama within the same arc also has it, so that's not much. "I knew Ace" is maybe becoming too much of a convenient shorthand for instant connection.
It was pointed out that she was in fact in Oden's flashback (or at least the pants were) so Oda conceivably had the character in mind a few months earlier than first mentioned, but that's hardly a "third sake cup shadow indicating Sabo" level of "Oda definitely was being sneaky here" situation. I'd feel more strongly if they were alluded to much earlier, similar to how Pudding was shown off years in advance.
Design wise, it seems like the horns are real (they were underneath the mask and multicolored) , she's very tall, she's got a little hair twirl at the top, and I think the hair fading from one color to the next is neat and fairly unique. Not unprecedented, Jinbe had the same thing going on when he was younger, and I feel like Ulti's hair stripes are a bit more unique I think. Oda put some thought into this design, but not a crazy ammount.
But oh man the Nami face is strong on this one. The eyes are different but... its very Nami. A stronger jawline or some cheekbones or something would make a difference, its definitely no Robin level of decisive facial distinctness.
So between the strong Nami face and the heavy Wano ties, I'm not riding this particular hype train, but its the most potential we've had in a character in a while. Devil fruit could obviously make a big difference. Strong secondary character to be sure, convenient to speed up the arc, not screaming nakama to me just yet.
If her main hair color ends up being white, purple, or red, that'll add some points though.