Use that live database replication along with LVM, Btrfs or ZFS snapshotting every hour and purging the old one. Take a full, proper backup every hour if you can or every day if you can't. If you can afford to, do a SQL dump at reduced priority and compress it instead of a binary copy as it's easier to check a text dump.

Anyone with more experience with large databases have anything to add or any concerns with this sort of scheme?