Should be possible. In fact, phase5 even asked customers what sort of expansions they'd like to see for the connector on the registration card for the 1260. SCSI was the only one they ever released, though.
The challenges:
-Market is limited to 1230/1260 owners interested in such an expansion - a small subset of a small subset
-Don't know if the appropriate documentation for the connector is available.
-You could achieve essentially the same result with a SCSI-to-SATA converter attached to the SCSI kit for probably less than a new expansion would cost
