Well, I'd argue that Roger Moore was problematic casting. He kind of works for the cheese-tacular style they were going for at the time (double-taking pigeon and whatnot), but quickly became very dependent on stunt doubles and couldn't really mack on nubile twenty-somethings without it looking super weird, even for the time.

If they're willing to just sign Idris up for 2-3 films then sure, he'd work very well. Bear in mind though that he's only 5 years younger than Daniel Craig, which is 1-2 films at the current rate.