Any reason not to try:
Most or all, except the owner who probably will never log on, vsftp users have rwx rights through group membership only.
Late Edit: So it'd look something like:
chown VSFTP_GodLikeUser:VSFTP_Group FTP_Directory
chmod 770 FTP_Directory <<------ I'm guessing here.
chmod u+s FTP_Directory
chmod u+g FTP_Directory
chmod +t FTP_Directory
Though I wonder if a user could write null to a file.
Late Late Edit: Never mind. I see the circle: u+s is crippled for what I want to do.