Lesse...
Vec: I highly doubt it would be him. I mean, despite the possibility of learning earth magic and soon discovering the ability to learn wind magic...but this is very difficult to pull off, considering the fact that during our first encounter with Sparrow, it was in the dark and he could see perfectly! If he had the side-effect of slow, it would be very big handicap for him. Vec IS an earth mage, for sure, in my opinion.
Kovak: No...don't think so, because Kovak's more or less too old for that job, so suffers from movement issues. I won't say much, but throughout the arcs, he does show signs of fatigue easily, and hasn't fought in a good while.
Barry: I...kind of think this might actually work out. Barry moved to EK's side, then hates S&S for them causing trouble for everyone. But then again, Sparrow appeared when they tried to open in Rellenia. This is also the same problem with Emma.
Violet: I...kind of doubt this part here, she has no reason for it, and isn't too keen on helping EK...but then again, who knows. We don't know that much about her.
P.S. Artbane, I want Arc 4...I couldn't finish beta-testing!!! X.x silly snag. I can't wait to play through normally.
Also, a treat for you guys, I'll tell you some interesting things I experienced beta-testing the game some weeks after it comes out. :p