User blog comment:Dave55811/"Coordinate" bets, anyone?/@comment-112.207.91.178-20140318170540/@comment-179280-20140318200719

As far as we know, the coordinate can be anything (barring Eren, since he's got the coordinate, and isn't it himself), but I highly doubt it's Mikasa. It's stated by Erwin that Eren's scream is what triggered the Titans into obeying him, and further proof is the aptly named Chapter 50.

Also, when was Mikasa mentioned being ill? I don't remember that ever happening, and I checked the manga not long ago. If you mentioned it because Grisha was periodically checking her when she was a child, well Grisha's a doctor, so it could be a routinary check. Also, the last time we know he went to visit her was because he was going to oversee the treatment of her marking (which was left pretty ambiguous in the anime, since her marking ritual was completely removed).

And yeah, I think you're right on the king. He looks pretty damn bored and it seems he doesn't even like being king. Maybe he steps out voluntarily once the Survey Corps get their plans working.