I would like to make a hardware component to replace the optical drive of PS2 by sdcard (or alike).
It should be doable if we know the full interface spec of PS2 optical drive interface, by emulating/supporting all the I/O call/opcode by software or FPGA.
I couldn’t find any existing project for PS2 but I do found some project for PSX and Sega Dreamcast.
I will probably start by replicating those project, and then embark one for PS2.
https://github.com/paulocode/picostation
https://github.com/zeldin/iceGDROM
(links are coded as raw text to workaround 2 links max limit for new members)
For the PS2 optical drive spec, I couldn’t find any datasheet (probably never will, because it is proprietary), but I do found some good info here:
https://psi-rockin.github.io/ps2tek/#cdvd
Since it is more fun and motivating to do a project as a small team, I am looking for ppl to team up and enjoy the ride together 
(In case you are interested, I have some mechatronics background but nothing close to pro.)