Is there even that much value to keeping multiple copies on the same device? I fail to see what this adds over backups which can be done with any filesystem.
Backups are better (if they actually get done, and if they are actually usable for recovery).
Backups + RAID is better yet.
But OP asked for a particular set of things that do not have any direct relationship to the traditional concepts of either backups or RAID, and ZFS can provide that set of things using copies=2.
It isn't for us to decide the value of this for them.
In a multiple device pool (with some redundancy) it would IMO be a extra and unneeded layer of protection.