This $0.02 is mine.
Not as the situation stands, no. The EN/SC devices are recognised through their drivers as NICs, not as local storage, and that only after an OS, and then the drivers, load and run.
Physically it ought to be possible in principle - I would be willing to bet reverse-engineering and rewriting the ROM in the EN/SC itself would be necessary, and possibly writing something special to run at the server end.
In the end it would be simpler to build a SCSI to network device from scratch (hey now .... ) - like a SCSI RAM disk that can locally cache a few-meg-or-less file fetched over Ethernet on request, and then serve it up to the Mac as a properly formatted disk. The homebrew SCSI RAM disk linked elsewhere would be a good start.
That would still only serve to netboot a single Mac, unless the device does some really fancy non-standard SCSI bus arbitration dance. And if you can achieve that, you might as well do away with the Ethernet part and just serve a single ordinary disk to the various Macs via SCSI.
The only other solutions that occur to me involve Nubus/PDS cards with speshul magik (as alluded to above), or re-writing the client machine's ROM.