Just a quick note about seven characters being "too much" to show in one direct:
An average character trailer is about 1-2 minutes, perhaps even shorter if they don't bother with a lot of story. Even Simon's high production value trailer was only about 3 minutes. Dark Samus and Chrom went about 1 minute each.
K. Rool didn't recieve any breakdown at the end of the August Direct, either, which saved a lot of time.
Assuming that every character is shown in one direct, Banjo, Isaac, Chorus Kids, Geno, and Mach Rider may all get unique trailers. I think it's safe to say that Geno and Banjo would get the longest ones, probably comparable to Simon's trailer, which is about 6 minutes so far. Isaac, Chorus Kids, and Mach Rider could be done in two each, and I'd even say you could cut that to 1:45 like Ridley. Ken and Shadow would be another echo block of 2 minutes.
When you put all that trailer time together, you're left with around 13 minutes of raw trailers. Another ten is probably all it would take to properly explain every character, which ends up at 23. Bump that to 25 for rounding, and out of a 40 minute direct that leaves you with 15 minutes left to explain the hidden mode and other odds and ends.
Yeah, it may be a double-sized direct, but it's entirely doable. The 50 fact video is only five minutes shorter than that. And that's already assuming they'll explain every single newcomer rather than pulling a K. Rool on them.
In fact, we're not even sure Mach Rider isn't an echo, so lump him in with Ken and Shadow and you save even more time.
It's not out of the question that we'd get a big blowout for our final presentation right before the game launches.