The "easy way" of doing this (if there is such a thing) to me seems like if you could wedge a hypervisor under OS/2 (or inside of it as the case my be) so you could run multiple instances of it, as if it were on KVM of ESXi but have it be totally transparent (or mostly transparently) to the user so it is all managed by native ArcaOS / OS/2 tooling in the UI and it appears like you are running one OS (think of the way virtual DOS machines currently work in OS/2).
I totally agree with this approach especially as multicore machines cries out machine partitioning as well.
If legacy 32-bit OS/2 would settle in VMs as DOS now (VOM = Virtual OS/2 Machine), then such old apps can use that, and new environment can be 64-bit, so memory management can move on enabling using physical memory above 4.00 GB.
Storage capacity itself can be resolved with network drives. That way OS/2 users can use any kind of filesystems those for there are no installable filesystem solution actually - e.g. XFS, OpenZFS, etc.
Also if you want RAID there, no problem if OS/2 does not support natively any raid device -- there you can have it underlying on the other machine. However I rather suggest LVM possibilities (on Linux) to add additional drive / copies of physical partitions when a new LV created for a filesystem. I got raid error on my home PC server once, and I could mirror / sripe on LVM layer more reliable than the risky raid stuff. In case RAID you really need a good, working backup/restore solution.
You don't need to use up many drive letters as you can mount them into directory as well. So the max. storage can be up above 48 GB that way.