More random, not necessarily related to each other, SCSI-CF thoughts...
A lot of basic IDE-CF type adapters will probably work fine as non-hotswap drives. It seems a lot more difficult to find a hotswap ATAPI memory card reader that works with the MPC3000, through a SCSI bridge. Hotswap may or may not be a desired feature for you.
The most common SCSI-IDE/ATAPI bridges seem to be the Acard bridges, not sure if your Yamaha bridge would have the same hotswap card reader compatibility, or even non-hotswap card reader compatibility, with the same card readers as the Acard bridges have.
When I get around to it, or someone else gives it a go, if it tests OK, then a SCSI-SATA bridge and SATA memory card reader might be another hotswap option for the MPC3000 and MPC60...

This SCSI-SATA bridge feeds power to the SATA CF reader, so it only needs a single power connection.
There is a version of the ATAPI 741 multicard reader that has a SATA interface, instead of an IDE/ATAPI interface, which might offer hotswap multicard support in the MPC3000 and MPC60 with a SCSI-SATA bridge.
It would be possible to place the SCSI-SATA bridge, or a SCSI-IDE/ATAPI bridge, right at the external SCSI port, and use the termination circuit on the SCSI bridge as a switchable terminator for when using, or not using, external SCSI devices. Then use a SATA or IDE cable of sufficient length to reach the memory card reader in the floppy drive bay.