I don't see why not. Though emulation would probably be easier on a few different levels - first because someone doesn't have to purchase/download it, secondly because the PSN only features a handful of titles.
as far as I know multiMAN still can't run legacy backups due to the soft rest the system goes through which resets any redirected mounts. you can use PS1 and PS2 backups on backwards compatible consoles using a few PS2 exploits though.
If you can be arsed taking it apart even basic disc swapping works for PS1 and PS2 backups.