No future development needed. Its ready to go
The Version 2.4a board can support this use case. I have a STL file for the bracket available here:
Fork of the original RaSCSI project by GIMONS. RaSCSI allows a Raspberry Pi to function as emulated SCSI devices (hard disk, CD-ROM, and others) for vintage SCSI-based computers and devices. - RASC...
github.com
PiSCSI 2.7 Fully Assembled and Tested (Previously RaSCSI Reloaded)
www.tindie.com
You could configure the RaSCSI to emulate a DaynaPort SCSI/Link and a SCSI drive to boot from. I've been using a RaSCSI inside my PowerBook 520c for a while and seems to work fine. (Just takes a while to boot up, since the Raspberry Pi needs to boot before MacOS can boot.)
Also - if you do this, make sure you disable the hard drive spin-down functionality. Whenever the Powerbook "spins down" the drive, it cuts power to the drive.