There is no generally valid way how to identify a CD-Rom, or in particular, a device a CD ROM could be connected to. Only those boards that come with an on-board SCSI or IDE might be able to support it. The CDFileSystem itself is ROM-able, though.
Even then, we are out of ROM space and the CDFilesystem does not fit in anymore (about 16K remains free). Before you argue "but we could have 1M ROMs"... well, we could not. The lower 0xE0 ROM space is now populated by the Vampires, so this option is taken as well.
How does ATAPIMajik work. That seems to detect fine.
Yes, CDFileSystem is romable but pointless, if it doesn't mount CD-ROM.
I don't own and never will own a Vampire, so Im not interested in it taking up space.
What about catering for both. People who use there Amiga as is and people who want to nuts on upgrades.