7-zip has the capability to create differential backups containing 'anti-items'.
When this option is used files that are not in the latest version of the source directory but are in the baseline archive are recorded in the differential archive in such a way that when unpacked they can allow restoration of an accurate snapshot.
This allows 7-zip to create archives that function in a manner similar to Linux's rsnapshot or Mac's Time Machine.
The documentation for this is here.
Any interest in including this as an option in Toucan?