I think it's very unlikely. In my opinion, the echos are purposefully chosen not only because they could work with another character's moveset, but because they have a reason to fight like their original. It would go against their very design to "de-echo" them. And it'd look weird considering how you can stack the echo on top of their original in the CSS.
I have a very different view on the Chrom argument, I think it's actually very weak. Honestly, I felt the speculation around Chrom being an echo of Ike was strongly biased, and that most speculators blinded each other. Chrom has no reason whatsoever to fight like Ike, he has a clearly different class, with Ike's being mercenary based, they also have no lore connexion at all, and they don't even wield the same weapon. Yes, they share some design similarities, and yes, they were compared in Palutena's guidance. But Sakurai stated Chrom was scraped because he would be a middleground between Marth and Ike, which wasn't as interesting as Robin using magic tomes. Then Roy came back, filling that space inbetween Marth and Ike. What's more, having him as Roy's echo links him with both Lucina and Marth, whom he shares a lore connexion with. Oh, and Marth and his three clones all have a very similar class in the game, which justify them fighting in similar ways pretty well. In my opinion him being Roy's echo, although it is indeed weird, fits him way more than echoing Ike.
If anything, Chrom's presence in the game could be used as a counter-argument to BK's playability. It would be a lot to have two echos from Fire Emblem in one game, wouldn't it? Anyway, I think the other arguments you brought up are actually really solid, and more than enough to justify the current speculation around him.