Bare minimum for daily backup

I know this isn't a legitimate excuse but with currently 7 TB of data being backed on this site, there is no room to accommodate a full GW system backup, so I am checking out (creative) options, but really I feel the answer is just to fork out the $$$ and expand the backup capability.

Here goes... If Groupwise users are all running in cache mode, and the domain directory is being backed up, but the PO directory isn't, Can the Groupwise system be fully recovered by reinstalling Groupwise with the old domain folder, then somehow importing user data back in from their PC's cache mode files?

The domain folder lists these files:
<dir> wpgate

If this idea is a compete no-go then I guess management will need to agree to an expansion of the backup system or live with the risk of data loss.

- Gordon