As Part of the AWSSKD NuGet package version 1.5.28.3 you can access a S3FileInfo object. I've used this in my S3 Storage File and updated the S3 Storage provider.
This seem to work, need to do a bit more testing on it.
NOTE: I had to add some code on the GetFile Method to ensure the permissions where set correctly otherwise the updating of thumbnails overwrote permissions on the file.... I'm sure there is a better way to do this.