I think the biggest complains of "too many FE characters" comes from the smash 4 days when a lot of people were thinking "they'll surely cut Ike like they did with Roy, he is not relevant anymore" leaving us with Marth and Chrom as a newcomer (Chrom was the most popular at that time). Everyone kind accepted that fate for FE since it was a dying franchise and they didn't expect Awakening to do so well and didn't expect Sakurai/Nintendo wanting to push the franchise in smash like they did.
Thus, here starts the "overepresentation / that character stole the spot of my most wanted" dilema, having so many FE characters a lot of people who were not fans of FE games and didn't thought the franchise was deserving enough were bothered by those thoughts, not realizing probably that Lucina cannot be considered a character (really, even before DLC there were already people complaining with the "but FE don't deserve so many characters!").
Then DLC came out and the smash team made the terrible mistake of bringing back Roy. I do think that was a mistake since we could have had Wolf back or another newcomer, yet they decided to bring Roy even though they were gonna give us Corrin too. That's were all the FE hate started to really flourish, and when they gave us Corrin too he/she was perceived as just "blatant advertisement" (which is kind of true) and not as an exciting newcomer (which he/she also is). And since the ballot thing was supposed to give people their most wanted character and they instead gave us "blatant advertisement 1" (Corrin) and "bad decision making 101" (Roy, even though people kind of loved Roy because he is a veteran, but still) well... The FE franchise was perceived as the culprit for not getting more requested characters even more than Bayonetta (another "blatant advertisement 2" that somehow was saved by them saying she was the winner of the ballot, even though now we know she probably wasn't and today she only receives hate for being a broken character in smash 4).
Back to today, the FE cast still have that stigma of "stealing other characters spot" sort of mentality that people like to have when it comes to smash speculation, even though that's not exactly how it works (kind of, I understand the complaint, but it's not that simple), much less when realizing that Lucina, Chrom, and unfortunately to some extent Roy are clone characters that shouldn't be perceived as any more than that.
Look, I'm the first one that likes to complain about the state of the Zelda franchise in smash and how poorly designed it is, but if you want to blame someone, blame Sakurai and his team for not wanting to do justice to Zelda for some reason, and also for not administering wisely the DLC spots. But the FE cast has no fault here and we don't have such a thing as "too many FE reps", specially when only 4 are completely unique.
Like, have you seen Pokemon? We have 9 characters 8 of which are completely unique and 6 of which are from Gen 1 and probabky we are getting another newcomer from 7 Gen, and nobody complains about that, probably because they love Pokemon. And on the other hand we also have the Zelda franchise with 6 characters, 3 of which are some sort of clones and from the 3 left 2 are the same character disguised, and people only complain about that when it's time to throw shi t to FE, not realizing that it is the way it is because this is the way Sakurai envisions the Zelda franchise and has nothing to do with FE.
So, cutting FE characters it's not going to do anything specially not when the characters they want to cut are clones, and makes 0 sense when the selling point of this game is "everyone is here".
You want more unique characters and not what we have for FE? I agree, but Intelligent Systems makes most of their protagonist sword users, blame them instead if you must blame someone for that, or blame society for liking more the swords than the spears/axes, cause that's how it works, they base their product on what they think people are gonna like. But anyways, in smash 4 we got Robin and Corrin, and even though they are both sword users, they are also both very unique additions that represent magic and dragons in FE.
There's no point in bringing for example Hector now just because he is a axe user (as much as I'd love for that to happen, it's not gonna happen) because his relevancy is absolute 0 and his popularity, while relatively high, it's nowhere close to enough. So, it's just a pipe dream. It's not the same case as other popular characters we've gotten until now. If you want another unique FE newcomer then push for Edelgard when her game comes out during the smash ultimate DLC period, as she appears to be an axe user.
Having Lucina and Chrom as echoes is really a blessing and we are actually lucky that they are sword users and that they have the same sword as Marth, because otherwise they wouldn't have made it to smash (and they don't take much development time, keep that in mind).
Having said all that, all I have left is to complain/talk about movesets, which I don't know if I should do but I've already written a lot so why not. So now entering into maybe shifting terrain (because knowing these forums someone is going to tell me they love full-on clones for whatever reason):
Roy should have been decloned completely. Specially since he was smash 4 DLC and they could have done him better. They could have given him a different side B based on his attack animation on his game, which would be a kind of acrobatic move (cannot explain right now, go check it out if you want). They could have also given him a different down smash, maybe thrusting the sword into the ground and releasing flames/an explosion to both sides. With those changes alone he wouldn't be perceived as a semiclone or at least not as much as he is now. Add some more fire effects here and there for a more unique moveset and there you go. I'd be satisfied with that.
As you can probably guess, given that we don't live in a perfect world, I'm ok with echoes, but I personally would like for them to have from 1 to 3 unique moves (or at least taken from somewhere else) to justify picking them over the character they are made from, from a gameplay perspective. Sure it would take a bit more time for them to develop that, but not much more and the game would gain a lot from it in my opinion.
Chrom is a good example of what I mean. He does not only seem to have a balanced blade like Lucina is to Marth, but they also gave him Ike's recovery and they Luigified that move. That's better than having him use Roy's recovery and is a nice variation from a gameplay perspective. If they went all out and gave him his own side special, it would have been perfect for me.
For Lucina, I would give her her own acrobatic move taken from one of the cinematics from her game. If they made the change to Roy I suggested above, they could even base it on that move with slight changes. Also, I don't think it makes much sense for her to have a shield breaking move since it's Marth's version of the blade the one that does more damage at the tip, so it's kind of iffy (right or am I wrong?), so they could give her something original there too.
Back on the matter of adding more characters, I'd like Black Knight to be an echo for Ike, and possibly Celica could be an echo for Robin (though I think it could only happen if they went a little farther with the echoes like I suggest, which is probably not gonna happen). I don't think people should be mad if these happen, since they are just echoes. I'm still sad by the whole "Chrom is too much FE" mentality. I'm not even a FE fan (I've only played 1 game) guys, wake up.
Edit: Grammar.