Look at it this way
Roy and Chrom have only appeared in one Fire Emblem title. What does Chrom have that Roy doesn't.
Multiple weapons, for one thing.
He actually has less than Roy.
Personally, I disagree.
Depends on who you ask, really. I'd argue that Chrom could be considered just as iconic, due to the fact that he's been in an actual international FE game which garnered much acclaim worldwide, and when the sales are factored in, many people know of Chrom. Therefore, he, too, is something of an icon. Sure, Roy is an icon as well, due to his Melee appearance. Although, it's not exactly "iconic" in that sense. His moves are pretty much Marth's, but with fire and poorer hit boxes.
this is true, but both are highly requested, you know. Off-topic, but II'm genuinely curious. If the requests meant that much to you, personally, why do you include Dixie over K. Rool on your rosters? Both are definitely requested, but K. Rool is much more so.
Debatable, as this relies on the individual's opinion.
and unique Fire Emblem character
Completely incorrect. How can you say that Roy is more unique when Chrom has never been in Smash, and when Roy was, he was a Marth clone?
and technically has had more appearances in the gaming universe (Melee, Awakening DLC,).
Which doesn't matter, really. The series has a fluid cast, and Chrom was the latest main character. Awakening's DLC had pretty much all of the past lords, so I don't really see how that's in Roy's favor. Chrom wasn't even thought of when Melee came out...this point seems rather moot.
He even had a prequel starring his direct identical relative which became the first international Fire Emblem.
True, but that really means nothing for Roy himself. It was Eliwood's game, after all. Roy got a cameo in the ending, and that's about it, if I remember correctly.
Roy was added over Leif in Melee because he was more unique (contrary to the popular belief that Sakurai ever mentioned recency had anything to do with it.).
This is true.
And Ike was added in Smash for being highly requested and having several appearances.
While the first part is true, the last part is false. Nowhere was it mentioned that having multiple appearances influenced Ike's playability. Sakurai didn't know who to add, and IS requested Ike, since he proved to be pretty damn popular.
So we know Sakurai has added Fire Emblem characters for being more unique and more requested/appearing.
The appearance thing is, again, false.
I don't see the point in having Chrom over Roy. Muh recency and Muh sales does not sound like Sakurai's criteria.
You're right, they don't. Good thing Chrom doesn't need that since he's popular and has the potential to be unique.
Why not add the character Fire Emblem fans are more familiar with, desire more, and has more potential and glory in the Nintendo universe? Advertisements? Adding a generic character who might as well just be any old Fire Emblem character years from now?
As far as that last bit, let's be honest. Would anyone really remember Roy, for example, if he wasn't in Melee? Or Marth, if he also wasn't as recurring in the series? Honestly, if the character gets into Smash, they sort of transcend to the higher plane than "any other Fire Emblem character." The boost in popularity from Smash pretty much seems like it cemented Roy and Ike's place in Fire Emblem. However, if, for example, Leif was chosen over Roy in Melee, Roy would more than likely be "just another Fire Emblem character." Getting the fanbase from both series generally sets the Fire Emblem characters in Smash apart from the others, in my opinion.
Also, just saying, I prefer the second roster of yours, since it has Starfy. In fact, I really like the second roster. The only things I'd personally change is K. Rool over Dixie and Chrom over Roy, but at least the two you chose make good alternatives.