Your signature lists a CSMK3. Its firmware already allows to boot from a CD drive which is connected to the SCSI bus. Just enable CD mount and CD boot in the firmaware menu.
Other than that, it shouldn't be too difficult to make a ROM module which allows general CD boot. IIRC IDEfix contains a program which allows to make atapi.device and CacheCDFS resident and boot from CD on the next reset. With the right knowledge it should be possible to turn it into a Blizkick module or similar.
Bye,
Thomas
