I'm running Samba 4 on RHEL 7, and we've come to a point where end users are going to need more control over folder permissions. 

My question is twofold:

1. Is converting my Samba setup to Active Directory the only (or even the best) solution for giving my end users finer control over folder permissions?
2. If yes, is it possible to take an existing Samba installation and set it up as an Active Directory domain controller, or am I looking at a reinstall? If reinstall is the only option, what happens to my existing database of Samba users, which is quite large?