Some questions to consider:

1. What kind of Windows Server security permissions does the identity running the SSIS package need in order to execute the WMI query? In a real world environment, I'd assume the file would be dropped to a separate server (maybe a network filer) which is where the WMI connection would need to be pointed, and my SSIS identity is going to be running with the absolute least privileges needed.

2. What is the impact to your SQL server if you have a long-running SSIS package (inside a SQL agent job, presumably) like in your example and you need to either restart the machine or the SQL Agent service? .NET Windows services have events you can handle in your code that allow you to gracefully stop your file watcher. Will the restarts hang when the SSIS package is sitting there? Do you have to manually abort the SQL Agent Job?

3. If a file doesn't get dropped for a couple days, what is the impact to the server to having a SQL agent job running for several days?