Whoo, seems like I missed all the um... fun. Partly because I'm tired and partly because I say this sort of stuff ad nauseum, here's all I've got to add:
I've said it before and I'll say it again - I can't deny that Robin is the most obvious choice to add much-needed diversity to the FE representation in Smash. He was one of my top 3 contenders for what I thought would be a single FE character spot, but I could never quite place him above Chrom simply because my kneejerk reaction when you say "main character" is "Chrom". Robin is absolutely super ultra important. I'd say he is Chrom's equal. BUT, because Robin has no true defined appearance, Chrom wins out by the tiniest margin as "main character" for me.
Mind, that is a really small margin. It's like the characters even say in the game themselves... they are two halves of the same whole. This is why my biggest pipe dream was for them to be a team character similar to the Ice Climbers. Then I wouldn't have to make that agonizing call which Sakurai obviously did make.
I do love that Chrom is part of Robin's FS because it really drives home what kind of a bond those two have. Fantastic call, really, especially when Sakurai could easily have just given Robin a high tier spell like Aversa's Night as a FS. For Awakening fans, it's pretty much the most symbolically significant thing Sakurai could've done and I'm glad for that.
Still, it feels wrong that Chrom does not stand on equal footing with Robin like I think he should. I don't like to have one without the other. And while Chrom is technically "with" Robin, the sad fact is that unless someone actually gets a Smash Ball, that's not going to be particularly apparent...I would just really love to see both of them as playable so they could truly tag-team. Yes, even if Chrom is not THE most diverse character we could choose.
Not gonna lie, I'd be simply beside myself if I could get a Chrom Amiibo and train him up to by my best little fighting buddy while I play Robin.