Why the F*** do you even want filesystem access? Wouldn't it be nice to not have to deal with all of that BS?
> being unable to download arbitrary content using a web browser
You've been able to do that since iOS 5 or 6, as long as you have an App that will handle the content you want to download, or a storage app that will let you manage and browse arbitrary content (See Dropbox, Documents, etc.)
> being forced to use a media player for system management tasks etc
Last time I checked, you don't need to use iTunes for anything other than transferring music & movies. You don't even need it to activate the device...