Allow differing retention policies for "chained" backups

We want to ensure that on-site and off-site backups do not run concurrently. We tried to combine forever forward incremental and "regular" backups in a chain, but no combination works correctly - if the cloud backup follows the on-site backup, it's not possible to use FFI. If the on-site backup follows the cloud backup, a full backup is never taken, and the on-site backup location eventually runs out of space. Ideally, I should be able to chain jobs, where there is a traditional "weekly full, daily incremental" for the on-site backups, and an FFI backup for the cloud. Alternatively, allow FFI for on-site/NAS type storage.