Hi Jennifer,
Typically if an organization/estate doesn't want materials to be publicly accessible, then they REALLY don't want people to have their own copies (this has been our experience at least). In fact, finding a way to disable any kind of downloading of an object's assets was proposed as part of the spec in the beginning, but due to the way the web works, if you can see an image in your browser it means you already have a copy :)
Despite my personal desire to make everything as open as possible, this module was developed so that we would be allowed to put things in the repository that we wouldn't have been able to otherwise. Since our goal is legal compliance and/or avoiding lawsuits, we've been a bit more conservative in our designs than we normally would be.
Despite all this, if we can find use cases where an org/estate wouldn't want materials to be viewable but they would be okay with them being downloadable, we could have a discussion about how to fold that functionality in to whats already there.
-Bryan