So it turns out there are really very different use cases for files. As the name implies, temporary files need never hit the disk and could thus even happily reside on a ramdisk (many systems clear /tmp upon reboot anyways).
For /home or /var many users might want a more conservative approach, e.g. fsync on close or something similar, accepting performance penalties where necessary.
I believe this is a larger issue and I'm glad the current behavior of ext4 receives such wide attention and makes people think about the actual requirements for persistent storage.
I'm certain in the long run the community will come up with a proper approach for a solution.