As the first priority of the inventory backup task, make possible full backup for full-perm items.
Assume a consensus on how to handle non-full-perm backup (especially non-copy items) will take time and not wait for that to happen before providing backup to full-perm items. This makes this sub-task have no excuses for implementation delay unlike the nonpermissive items backup...
The earlier implementation of full-perm-backup could save some large number of users most of their inventory, and the full inventory for content creators since they have full perms on their creation; this makes this sub-task significant for the economics and stability of Linden Labs and content-creating businesses.
P.S.: Part of the backup should be encrypted to make sure no one without creator status gains it just by editing the backup! Yet the backup parts of objects created by an account should be nonencrypted to make export to other software of any kind really easy!
P.P.S.: as backup might be ressource-intensive, it's perfectly logical for Linden Labs to put some kind of restraint on it so no one can lag entire sims just by backuping nonstop.