I would certanly like a CD/DVD-Emulator, esp. with disc-changing solution by choosing the image like on a gotek.
But actually there is not a real demand, because it is not true you can not buy new produced optical drives with IDE/atapi. SATA actually is mostly a serial version of IDE; a transperent conversion between IDE/Atapi and SATA is no problem at all. Such an adapter only cost about $4 incl. shipping (https://de.aliexpress.com/item/1005001790344824.html). So you can use any actual modern optical drive inside your vintage PC.
Many people are "collectors" - and as people like to collect and streaming does not fullfill that, CD´s and blue ray sellings might go down due to streaming, but will not stop. Pressed optical mediums have a quite long live. Same as with vinyl being still produced - and still also the drives. In lower numbers, but they are.
Due to the backwards compability (you can use any blueray drive to read CD and DVD also) there might be a drop in sales - but no end in sight for the medium as for compatible drives. Also no end for SATA in sight.
So the situation between emulation of Floppy drives, where some media like Double Density (instead High Density) needed for popular vintage computers like Commodore Amiga or Atari ST are not produced (and still produced Disc Drives might read DD but can not reliable write them), is quite different to the situation on optical drives or even harddisks (where on IDE quite cheap IDE2 CF, IDE2SD, IDE2SATA or mSATA-Adapters are available).
So an Floppy emulator is mostly a must2have to use popular vintage computers (and play the games you loved as you where young). So it is a mass product.
IDE-Hard-Disc Emulation is no problem anyways.
Simulating SCSI is much less needed, but for vintage Apple users often is essential. Much smaller numbers as on the more sold vintage computers, so less demand. Also as SCSI is much faster than Floppy, so more powerfull controller needed (like an rapery pi zero with level converters, emulating a scsi interface at the GPIO - but boottime of the Pi can be a problem with timeoff on start. So more comfortable are FGA-solutions). So DiY solutions starts about $30 (with a little problem on instant boot) and $90 for "ready to use" SCSI2SD.
Emulating MFM HD is quite less needed, emulating more complicated, uses FPGA and cost more than 200$ (as it only is produced in small batches). But there are cases they are needed, f.e. if you have a programmer for SPS Controllers, like the Siemens 750 (wich is a 386 portable PC with 8 inch tube monitor and programming interface for Siemens SPS controllers, but a bios only booting from Floppy or MFM controller).
But emulating optical drives is not a must2have, but only a "nice2have" for very few people. As modern optical drives can be used extremly easy (at least on desktops) only some vintage notebooks might require it. But still, if you are a fan of a vintage notebook, you mostly want it most stocklike as possible, and you still get CD-Drives used in good condition. So using an emulator (wich has to fit inside the IDE/ATAPI-CD-Drive by the way) is not an urgent problem. Maybe the demand increases in 10 years.
Of course an emulator for CD-Drives is nice. I would certanly buy one, if it has CD-Changer Emulation, as I always wanted a CD-Changer for my Amiga (CD Changer are hard to get now - and quite expensive, so $200 for an emulator would be less than an real one). But a "drop-in" solution would be a product only for few people, produced only in small numbers and at a price quite high.
I mostly hope someone designs an "IDE-Emulator" for the raspberry pi zero (W) like the existing "SCSI-Emulator". It would be a 30$ solution hardwareside. Even if boottime for IDE is problimaticaly (SCSI scans much longer for drives, so with SCSI ID 15 good chance Pi has booted already after power on the computer). On IDE time for starting the Pi exeeds the scanning time for devices. So you have to delay power getting from PSU to mainboard by about 20 seconds using a relay to allow the Pi to boot before starting boot process. Also I am not sure DMA-Mode can be simulated on GPIO. But for a vintage computer, PIO-Mode would be more authentic anyway.
Of course you can use the PI SCSI emulator in combination with IDE2SCSI converter (Haage and Partner if I remember correctly). But while the SCSI emulator is cheap, the SCSI-Converter last time I looked was about 350$. I bought one (or two, I am not sure) more than 20 years ago for about 50$. I thought that being a high price than... But of course, as I said, price gets lower as more is sold. The time I bought it, large numbers where produced and sold, as the new upcomeing IDE took over SCSI. SCSI-Drives where much more expensive at the time, more than double the price for IDE-Drives. Als the demand for bigger storage never ends, many people with a existing SCSI system wanted to use IDE devices. Even with 50$ such an adapter + IDE-Drive was less than buing a SCSI drive. If I remember correctly I bought the adapter witch worked in both directions (SCSI->IDE and IDE-> SCSI).
Ironicly, I used the adapter for adding a CD-Drive to the SCSI bus. Would be funny if I find it again and use it for adding a SCSI-CD-Emulator to IDE now. But most likely if I find them, I will use them for restauration of my old Amiga 2000 (as the SCSI harddisk would most likely not work by now anymore, but I need the SCSI-host adapter anyway, as it also contains the RAM Expansion...)