I'm not sure that any potential advantage that Brimah might convey on offense is enough to overcome what will certainly be a disadvantage on defense, since he'll have a hard time keeping up with someone of the handle and shooting ability of Melvin Ejim.
Actually, with Niang out, this is the type of game Brimah could thrive in on the defensive end of the court. Niang's absence has pressed Daniel Edozie into duty, a virtual zero offensively. Edozie played 16 minutes for Iowa State in Sunday's game against North Carolina, recording no points on just two shot attempts. Ideally, he's just the type of player you want to stick a shot blocker on - somebody who allows Brimah to roam the paint and swat shots out of mid-air. You don't want Brimah guarding somebody like Georges Niang, a player capable of stepping out and nailing shots from the perimeter.
Of course, I'm sure Iowa State will also play a smaller lineup - with Hogue at the four and Ejim at the five, or vice versa - for large portions of the game, in which case, you're probably right, we'd be better off with Brimah on the bench. Regardless, I don't think people understand how Niang's absence alters the complexion of the game. Him being out is every bit as significant as Kane or Ejim being out.