I'm very rusty on that, but would playing with the /D option help?
What I mean in config.sys whatever driver you need to load, should have the option to name it via /D:CDROM. Then in autoexec.bat use the same option (mscdex.exe /D:CDROM)
(for both drives don't use :YOURNAME or add a second /D:DVDROM

OR tinker with LASTDRIVE= to make sure that mscdex cannot assign an additional drive letter

What happens is, both get the same name just with a different device ID.

So if you have /D:DVD-DRIVE you will get DVD-DRIVE#0 and DVD-DRIVE#1

I like the idea regarding LASTDRIVE 😀

Will test it...

Bugger. If there aren't enough driver letters, MSCDEX refuses to load entirely...

Found this in a readme for an XCDROM driver:

/PM Requests the driver to check the IDE primary-master unit for
a CD-ROM drive during driver init. If a CD-ROM drive is
NOT found as primary-master, driver loading will ABORT!

Exactly what I need?

Sorry, all I could think of. That xcdrom option sounds like it could work.
Have you checked freedos' mscdex?

Well it worked in term of being able to only load one driver.

BUT this driver is totally useless when it comes to games with CDDA. Doesn't support CDDA Volume control, so Pinball Illusions will play CDDA and Sound Blaster music simultaneously and Descent 2 also doesn't play CDDA.

So I guess I keep hunting for another driver 😀

Any luck?

I was getting ready to try xcdrom.sys as a way of freeing up a bit more conventional memory, and found this thread while searching. Guess I can save my time on trying this one out. Kind of hoping that maybe you had come across something that works?

No I use the IDE channel trick. One drive on each channel, disable, enable what is needed. This works flawless 😀