Crossing the clone talk with the Kirby talk, what are everyone's thoughts on Galacta Knight, Morpho Knight, and Dark Meta Knight?
Galacta Knight arguably makes the most sense at this point. He's the most reoccurring of them and is typically seen as MK's biggest rival of these three. I know that using a lance seems weird for a MK clone, but that hasn't stopped HAL from using Galacta Knight's lance the same as MK's sword.
Morpho Knight seems to be the up and coming replacement for Galacta Knight, though. After semi-killing Galacta off in Star Allies, he seems to be the new go too EX MK after retuning for Forgotten Land. He's also just a touch easier to implement as well as a clone.
Dark MK I'm mostly going for completion. He seems to be semi-reoccurring after Star Allies brought him back and these days seems to be the go-to representative for when they want to reference Amazing Mirror. Obviously, he's so similar they might have to work harder to prevent confusion between Pit and Dark Pit, though I at least can think of one way to make it easier (keep his wings always out like the modern games).
Personally, I always feel like an MK clone always has a dark horse chance, with Galacta as the front runner, but I'd like some other opinions.
I don't think any of them are super likely just because their appeal is extremely similar to Meta Knight for the most part, and there's also the strange aversion to adding things that are newer than Kirby Superstar, but if they do go for it, I think Morpho Knight is the only one that they would go for:
Dark Meta Knight is just Meta Knight without a code of chivalry, and while you could have some cool flavor animations involving mirrors, there's not a whole lot to differentiate them since Meta Knight's code of chivalry isn't even present in the series. The closest you get is his "come back when you can put up a fight" line, which would work in the opposite direction too. Arguably, it works better. Without giving him his moveset, I'd say he works best as an alternate costume.
Galacta Knight has problems since he seems to not be entirely cannon, and he lacks a Dimensional Cape, so his down special would have to be something else. With how he animates, he seems to be more of a paladin than a duelist, so there is that to differentiate them animation wise, but just having him do Meta Knight's moves doesn't seem super fitting, especially since the main thing about him is that his attacks are super extra.
Morpho Knight kind of falls in with Galacta Knight in how extra he is, but instead of summoning a screen spanning tornado, his main standout attacks are a teleport (which give him an easy replacement for Dimensional Cape since he also doesn't have one), and making his swords really big, which could be pretty easily implimented as an easter egg that happens when you charge his smash attacks for a silly amount of time.
As fun as any of them could be, I don't think they'd actually do it.
I think Samus is gonna be based on Samus Returns due to Prime 4 releasing too late.
Costumes are different than whole characters. They can take any design that's been finalized even if the game is unfinished. For example Xenoblade Chronicles and ARMS came out a year before SSBU, and missed the boat for characters, but The Legend of Zelda: Breath of the Wild released the same year and got a visual redesign and moveset tweaks for Link, music, and an entire stage.
IIRC, the Wooly World stage on SSBWiiU came out before Yoshi's Wooly World. Things like that aren't going to be as much of an issue, so it's really a toss up for which design they think is more important: Metroid Prime 4 or Metroid Dread. They could even have both as kind of classic and modern design alternate costumes.
Also, Metroid: Samus Returns? Is that what you meant to say? Why that one specifically?