Replication will be essential to a valid CIFS/Samba implementation. We will need to replicate several things including the login scripts between servers. Since we have to do this anyway we have the opportunity to make extended methods for syncing other types of data between servers. This includes user private keys for OpenVPN, profile data, file services data, and other such data.
Sync services will need to have good controls for resolving conflicts or have prioritization processes for authoritative data. In addition, the sync services should also use encryption and data compression mechanisms. They should also transfer data via delta blocks and have tunable controls so as not to soak bandwidth pipes.
We may find an applicable technology that can be implemented easily to handle this or we can use rsync.