The special Shared folder will be gone with ownCloud7. ownCloud7 will place the shared files/folders directly in your root, from there you can also rename the shares or move them around.

Generally you describe the way sharing works in ownCloud correct. Sharing is the concept that userA wants to share files/folders with UserB/GroupC. So the owner will always be UserA but he grants access to it for additional users.

What you are looking for can probably achieved with the external storage app. This app allows individual users and the admin to mount additional folders to ownCloud. The app also supports local storage. So you can mount a folder somewhere else on your server to ownCloud. If you set up the mount as admin you can define which group of users should have access to it and ownCloud will place the mount point into the data folder for each of them. That's probably more or less the use case you are looking for.