Hi,
Remembering from the old time with OS/2 Warp 3 on a PS/1 with a TEAC CD-55A CD-ROM drive using a Mitsumi interface if I'm correct. The CD-ROM drive needed a driver for it to work in Windows NT 4.0 and OS/2.
For OS/2 I made a copy of the install floppies and added the needed driver taken from a OS/2 driver CD that had it. The hardware identification and configuration is made during the floppy disk step. So if you can find a driver for your external parallel port CD-ROM drive, it may work. I still have the drivers CD, if you want I can check if I have the driver for it, it should work for Warp 4. I think the Micro Solutions Backpack is using an internal Mistumi connection and a chip that do the translation between the CD-ROM drive and the system. So it requires a compatible CD-ROM drive (160550 and 162550 units for example), but from the system point of view, the driver need to be for the controller chip that do the translation.
Let me know if you want me to check for the driver.
You can also try to install it from floppies REMOVED and then use the CD to install the bonus content. That require a lot of time and two computers to optimize the creation of the floppies or a lot a floppies created at once.
Addendum: Maybe it is possible to install Warp 4 from a HDD, but I don't know how to do it. But I think it would require to edit installation scripts and may require a FAT16 partition and OS/2 take full advantage of its own HPFS format. Meaning a lot of work and headache.
Knowing things is great. Understanding things is better. Creating things is even better.