Sticky bit set for a directory is a mean for "Restricted Deletion" — according to manual:
For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp
The thing is it has rather a very wide scope; only root
user is excluded from its scope.
Can you suggest a technique to get "restricted deletion" applied to specific user (or a group of users) only?