We were discussing the film's casting at the weekend, and at that point, Hugh Laurie, Ken Watanabe and Alan Rickman were all under consideration for a particular role. I'd expect, in fact, that it was this one.
John C. Reilly, if he signs on, will get to share scenes with Close as another member of the Corps.
In the comics, the head of the Corps. was Nova Prime. While the name might stick in the movie, a lot of the details will have changed.
Deadline are assuming that Close will be playing it tough, and that's certainly something she's done well before, but I wouldn't be entirely sure, just yet.
Close was last on the big screen with Albert Nobbs, which was something of a passion project. Guardians is likely to be a rather lighter gig, both in terms of emotional commitment and shooting days, but I'm still pleased that Marvel made this match.