Right - that's Unix "inside the box" thinking. The idea is to make the operating system smarter so that the user doesn't have to deal with what's computer friendly - but reather what makes sense to the user. From a user's perspective if you have not rights to access a file then why should you be allowed to delete it?
Now - the idea is to create choice. If you need to emulate Unix nehavior for compatibility that's fine. But I would migrate away from that into a permissions paradygme that worked like Netware.
I started with Netware and I'm spoiled. They had it right 15 years ago and Linux isn't any where near what I was with Netware and DOS in 1990. Once you've had this kind of permission power Linux is a real big step down.
So - the thread is about the future so I say - time to fix Unix.