I suppose you could store a mapping of AMI IDs to default user names in the script, but this would add a lot of overhead when it comes to creating and releasing

I suppose you could store a mapping of AMI IDs to default user names in the script, but this would add a lot of overhead when it comes to creating and releasing new AMI versions. How about using tags to store the default user name for each AMI? Then you could modify this script to look up the username before connecting.