I need to install FTP server in my company for file sharing, backup, and archiving.
I use CentOS 6.4 64bit and the latest version of vsftpd.

I was able to install and do basic configuration of the vsftpd FTP server, that is:
- Set up a couple of virtual users who do not have the permission to access anything but their home folder and its content, using this guide vsftpd: Local And Virtual Users With Bash Scripts For User Maintainance (CentOS 6.0) | HowtoForge - Linux Howtos and Tutorials
- I installed the certificate and enabled the use of SFTP .

I'd like to make vsftpd server do the following:
- There are three groups of users, so that each group has some number of users. Users have theirs own home folder, which are located in the home folder of the group, which are located in home folder of FTP server.
- User Nick (rookie) can't leave his home folder, and user Chris (senior staff) has permission to see the content of group's home folder /var/ftp/groupa2, but he doesn't have permission to change folder in any way.
- Other than administrator, there should be another user, director, who has permission to access, delete, or change files and folders in subfolders of all groups and users, but he shouldn't be able to leave the /var/ftp.

- This is how it should look:
/var/ftp/ - server
/var/ftp/group1 - home folder groups
/var/ftp/group2
/var/ftp/group1/nick - home folder users
/var/ftp/group2/chris - home folder users

My questions are:
- Where should be the location of director's home folder?
- How can I make groups of FTP users in vsftpd when using virtual users? And how can I join virtual users to the group?
- How can I make each group has its own users who can access a group folder and theirs home folder which is a sub folder of group folders?
- Is it possible for a user to be a member of several groups? If possible how can this be done?
- Is it possible to enable user to read, write and delete files in his home folder, and to have only read only permissions in his groups home folder? If yes how?

Any help will be much appreciated?