In regards to the vast number of Fire Emblem characters, I don't see the issue with people being against the idea of adding even more. For me, I just want to see other series get that same level of treatment. Some series are just now getting new characters when they haven't gotten any since Brawl. Some series are just now getting lost characters back, and likely won't receive another character. Meanwhile Fire Emblem has gotten a character back as well as three new characters since Brawl, and there's still the possibility of even more being added. I don't see anything wrong with wanting the attention Sakurai pays to certain series to be spread out a bit more across other series.
In regards to Pyra, she'll most likely end up being toned down a bit if she and Rex make it in. Probably reduce her breast size and/or give her a sort of undersuit to cover her thighs and back, like that of Corrin and Bayonetta. To be honest, I don't care much for Pyra's, or Rex's, designs myself, so I wouldn't care either way if Pyra got covered up or not.
Lastly, in regards to Vergeben, just because he's gotten plenty correct thus far, that doesn't mean everything he says will come true. Remember, not all the information he gets comes from the same source. His source behind his first leak seems to have been accurate, but that doesn't verify the 'leaks' that have come afterwards, since they appear to have come from different sources. Time will tell if he'll continue to get things right, or if one of his sources ends up being wrong.