Data security will depend on making sure that all accounts have the minimum rights needed, and that there is no dynamic SQL. Application accounts should have no direct access to database tables.
Security maintenance should be fairly easy. If no changes are made once the system is secure there isn’t much to do but make sure that nothing changes.
Same goes for replication. Once it’s setup it is usually pretty much a set it and forget it system, unless you have a very complex topology with very slow LAN/WAN links.