My initial reaction would be, yes, it would complicate things. By bringing in the concept of imminent, it would create issues on how you meet that definition and how that would be prescribed. It's much easier to keep things open-ended in case the minister needs to take other kinds of actions for other kinds of threats if necessary.
I'll just say as well that the Minister of Transportation also retains a broad discretion in this area as well, in terms of ability to direct air carriers to do things that are reasonable to do regarding security.