It's not possible to do what you want with iTunes, or even iCloud.
It's either all or nothing and one of the things I hate about Apple forcing you to use iTunes to sync content, apps and data.
It may be possible to extract something with third party software and then using other third party software browse the limited file system access and drop in the content. I've done this in the past to force video into the video app as well as force my photo database to restore.
Not sure if you can access parts like for voicemail or text messages though.
I'd just do a Google search. There are a number of third party applications for Mac/PC that allow access to the file system and backups out there.