How does that list indicate that Petey, R.O.B., and the Primids (I'm assuming that's what you meant by 'Emissaries') are going to be playable? If anything, it's indicative of them not being playable characters.
Characters that there are multiples of (Polygon team and their replacement in Brawl, Primids) are never playable, without a gameshark or AR. That also rules out R.O.B.s.
A character like Petey is far too large and powerful to be playable. His tongue is bigger than Peach and Zelda. He can hold two characters with ease, he shoots out giant balls of sludge, and he can petrify his opponents. I have a good feeling he's going to be a boss.
My point is that I've noticed Smash games have a tendency to get a lot of mileage out of the character models and animations that are created - think of all the clone characters and the way so many things were cleverly reused in Event matches (resizes, dark link, etc).
This observation isn't an "indication" of anything, but it helps a little. You've given some points about why they may not be playable. I think it's possible that they will be playable, but I am far from making a bet on it.
Oh, and don't forget you can control Giga Bowser in Brawl. He's pretty big.