Okay, my thoughts on this are complex (not least since Echoes exist on the grace of being easy to add):
Ken's completely fine, and so are Chrom and Lucina. My motto when it comes to echoes is "Is there a gameplay-related reason to pick the Echo or the original? Or does it practically not matter?" since all Echoes have a personality-based reason to pick one over the orignal. That said, it'd make a lot of sense why Chrom and Dark Samus did well on the ballot, and decloning them further could be beneficial.
However - for those aformentioned gameplay reasons, I'm leaning towards Dark Samus and Dark Pit.
The gameplay related reasons for each of the four remaining echoes are minor but I feel a little miffed by the fact that they didn't go further (I have to assume time constraints, but still):
has a faster roll but it leaves it vurnerable due to the lack of Morph Ball, its Smash attacks and projectiles hit lower, the missiles' start up animations are more ambigous compared to Samus, it has different hurtboxes when moving around and fire's replaced by electricity etc. All of these combined don't amount to a different character though (outside of really specific interactions like an uncharged shot hitting a crouching
where Samus' would not). And none of those give off the impression of the ruthless monster from the Prime games either. So yeah, make her a bit more reminiscient of her dangerous Phazon form pls.
... the different arrows do make a good case for one or the other: Pit's are more maneuverable, can cover loads more angles (it takes practice though) and can tack on damage / snipe more easily off stage, Pittoo's are faster, with stronger knockback and thus kill more easily. Upperdasher / Electroshock? They do the same thing, just kill off the top / side respectively (although its reflection property could use a fix,
wtf why did they design the reflection property to follow weird angles: )
And yes I know they have Guardian Orbitars to take care of that, but it's still ridicolous.
And the arrows are the only meaningful gameplay-related reason to pick one or the other. It's a missed opportunity, especially since Pittoo's been in two games now.
While both Pits have some weird inconsistencies in their movesets (one of which being N-Air's weirdly small hitbox and I'm not entirely pleased with that -
inherited that too just to make me question things even more) I honestly feel that Dark Pit could benefit from utilizing Uprising's different weapons more thorougly. Not least since Pit does represent the standard weapons pretty well.
Also, for Daisy / Richter? Numbers changes can do a lot of work, even if I'd prefer some moveset changes for them both (give Richter Hydro Storm as final smash pls). Yeah, animation changes would also help but that might inch towards decloning, and I'm keeping my choices to the Dark counterparts. Daisy could benefit from more ground centric stats and stronger attacks compared to Peach in exchange for weakening the float so that she approximates the Mario Sports games more, while Richter could benefit from having the moves that originates in his games be stronger in comparision to Simon and Simon be stronger with the moves he debuted with.