Funny enough, I had the same experience this morning with the same player. He joins missions (the two times I saw him, he was hosting and had a terrible connection as well), and then goes AFK the entire time. He's definitely there because he had to actually join (or it would have canceled the mission), and if you manage to win despite him being a total burden, he picks a prize. Being able to kick people like that (and people that lose on purpose) would be great. Had a similar issue with a PC player named ******* yesterday. He would join, vote to surrender, and when everyone else rejected the vote, would throw himself off of cliffs or gets others killed on purpose. Ruins the game entirely.
One thing I'd like, since some people seem to think that others would somehow 'abuse' a kicking system, would be to let us see the names of who we're joining before we're locked in. Because when I see either of those two names in the character select screen, I just leave...but then I'm stuck waiting for them to finish ruining the match before I can play again.