filesystem permissions + user management

[ro]

Hi,

I have to set up a gentoo box with some features that seem a bit tricky to set up.
1.) Some users (operators) should be allowed to add/remove users, but only users they have created (operator A should not be able to administer the users of operator B)
2.) The users created by the operators have ftp access (via vsftpd). However, one of the operators asked me to set up restrictive file permissions: the users he has created should not be able to delete files they have uploaded.

Concerning the 1st challenge I am thinking of some sudo rules, but I am happy with other solutions (RBAC,SELinux, other hints?), and for the 2nd I have no idea yet.

thanks in advance
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