Lots of interesting characters in Three Houses, but some of them would be a little difficult to translate into interesting and reasonable Smash characters. Some are likable but don't seem like they have the personality of someone who would go and fight in Smash Bros happily. Byleth might be the most likely but Byleth has little to no personality and has a pretty traditional moveset so she would be pretty boring compared to the others.
And we're not voting for most likely, but most wanted.
And we're not voting for most likely, but most wanted.