I like your lineup as is.
I will tell you why I wouldn't play the others.
Cobb: His production has slowed as of late, and Jennings is coming back this week. I would give it a week to see how it all fits together before I make a choice on that.
Blackmon: Well... I can't tell you anything bad about him. Good rookie with tremendous upside with a favorable matchup. I just think that the other matchups are better. If I were going to start him, I'd probably replace Brown. If only because we only have one game worth of starter info on him, and we've seen that the Indy D can be suspect in a few games.
Fred Jackson: Splitting time with SPiller, I just don't think he'll get enough to help.
Vick Ballard: I think he is overhyped. I've yet to see him perform well enough against the projections to make him a starter. I have him sitting on my bench as well, and he will probably sit there the rest of the season.
T.Y. Hilton. He is very sporadic. VERY sporadic. I like his big play potential, and he's had a few games where he has really been dynamic, but I'm not sure if we are to the point where he is going to be a consistent start over someone else.
Felix Jones: of the players you listed, I would rank him only ahead of Ballard and Jackson in terms of starter quality. You have a good lineup.