People tended to be fine with FE's representation up until Smash 4's DLC methinks. Or maybe just until Corrin? I said it before Byleth got announced, but I think a FETH rep would have been requested pretty heavily if Corrin simply wasn't there, maybe even with Roy and Chrom still padding FE out. Ultimate's Everyone is Here goal would have made it that Roy came back regardless of what happened with Smash 4's DLC, but I think people would generally be okay with Marth/Lucy, Ike, Robin, Byleth, though maybe Roy being in there too would have been pushing it.
I'm trying to think of a "balanced" FE roster, and its difficult. I want to represent the older games (1-5), the GBA games, the Tellius games, the 3DS games, and then TH, but in the end the best I can think for that would be Marth, Lyn, Ike, Robin, and Byleth. That's all sword users, but I think that's just what FE has to be the more I think of it unless you want to throw in characters that are less important simply for the sake of their weapon, which I don't think is a good idea. From a gameplay stand point, Marth, Ike, Robin, and Byleth all are different despite the swords, and Lyn would probably work out well with a flash quick draw movest. Anna I suppose would be my pick for a sixth fighter though, and for her I'd hope specifically she wouldn't be using a sword primarily. Maybe a staff, though she should still have the Levin Sword's long range bolt.
