I have an unsupported CD-ROM drive, but I was able to patch a kernel with support for it, and I replaced the kernel on the RedHat boot floppy with my kernel. This kernel does recognize my CD-ROM at boot; however, the installer won't let me do a CD-ROM install because it wants to find a CD-ROM driver module to use with it (and loading these modules fails, since I have no such drive). If the installer allowed me to skip this (and switch to a virtual console, so I could create the appropriate entry in /dev), then I'd be set.
The installer can't let you switch to a CD-ROM then, because there's no shell to switch to (no space on the boot disk.) You'd have to patch the installer.