I haven’t tested it myself, but perhaps one solution would be to use PKWARE’s product: PKZIP for iSeries, ver 5.6. I believe it can compress the save files efficiently and the max file size limit for input/output files is quite large, I would think.
Check PKWARE’s web site:
You can also download and test the free evaluation version from there.
Actually I was also thinking a same kind of solution a while ago for my customers, but these (2) customer’s have both upgraded to larger iSeries systems, so that the storage problem is, at least so far gone.