Is your feature request related to a problem? Please describe.
Timeshift has a feature where it will execute scripts located in /etc/timeshift/restore-hooks.d after restoring a snapshot for both Rsync and Btrfs modes. This mechanism also exists for when creating snapshots and while Timeshift has backup hooks implemented for Btrfs, the same cannot be said for Rsync. I think this feature could be useful for Rsync as well, since it would be helpful for overcoming some of the limitations on non-GRUB2 and non-Btrfs systems. Implementing this would also make the Rsync mode reach feature parity with the Btrfs one.

Describe the solution you'd like
Basically the same mechanism as Btrfs. The restore hook mechanism for Rsync and Btrfs are identical, so there's no need to make it any different.