sftp user with ChrootDirectory

Dear All

I have succesfully created a number of sftponly users with:
"ChrootDirectory /app/%u" option in sshd_config file.
So under /app there are the home dirs such as:
/app/user1, /app/user2 etc etc.
permissions on /app and /app/user* are as expected (root:root and 755).
So far so good and everything is working perfectly.

Here is the tricky part when Application owners want rear/write permissions under /app for user lets say "thomas" who belongs to group "fincance"..actualy they are asking to "chown thomas:finance /app"

If i apply this then sftponly ownership rules are violated....

Any idead how can i bypass this rule? or implement such a request solution?

Note that using another directory for either sftp or "thomas" user is not an option, /app must be used....

Many thanks in advance.

D.A