I'll be honest, I don't see any of these similar moves that you seem to see. But hey, it's grainy video and opinions are opinions, so I won't argue that point. But I will contest your claim of REPLACEMENT.
I think we need to define our terms here. For me, a replacement is something that can serve a near-identical role to that which it replaces. To quote the dictionary, a replacement must be able to assume the former role, position, or function of the thing being replaced. Now, under this definition Ike can't in any way be Marths replacement, because as countless hands-on experiences have shown Ike is flat-out incapable of occupying the same role (as nimble swordsman), position (as top tier), or function (in terms of having a similar moveset, which despite your protests he doesn't) as Marth.
Now, the definition of replacement YOU seem to operating under is a much more generic blanket-term that seems to be 'anything in a place previously held by something else'. So under your rules Ike can replace Marth because he can occupy the space of sword-wielder from Fire Emblem.
Not to put too fine a point on it, but I think we should use my definition of replacement for this one. Because under what seems to be your definition, Poke Trainer could be considered Pichu's replacement (assuming Mewtwo and Jiggs return) on the grounds of being the fourth Pokemon character. And calling Poketrainer a replacement for Pichu just doesn't make sense.
Now, if you want to argue that Ike will be similar enough to be able to play like Marth, and is thus Marth's replacement, be my guest.
If you want to argue that Ike is in and Marth will be cut just because Marth will be cut, that's fine too.
But don't argue that Ike is a replacement for Marth if we know that they can't play even remotely the same. If Ike can't play like Marth, then he's not a replacement, he's just another Fire Emblem character.
Edit: Oh, I just remembered. Ike's supposed Marth costume? Not Marth's colors. Marth has a light blue shirt and dark blue legs and gloves. In Ike's 'Marth' costume, the legs, arms, and pants are all white. These are Sigurd's colors. That's Sigurd, not Marth.