RPCS3 PS3 SA-CD reading and writing functionality

I am curious if it is possible to emulate the first two generations of PS3 consoles, namely the 20GB and 60GB first released models?

RPCS3 doesn't emulate the hardware directly. Nucleus does that, but it's long ways off from being working.

But more importantly my interest is reading SA-CD discs and writing them as well using my Blu-ray writer or possibly even a DVD writer in Windows XP.

We can't support something in software, that hardware can't support. See the SA-CD Wikipedia page for more information. RPCS3 ain't a disc reader/burner, look elsewhere. RPCS3 only supports 64-bit OSes, so XP is a no no. I don't think we officially really support Vista either.

CECHE also works but PS2 hardware compatibility was dropped so I'd rather not go to this model's ROM because I'd like to see this emulator have PS1/PS2/PS3 compatibility rolled into one.

RPCS3 is a PS3 emulator/debugger. PS1/PS2 compatibility is out of question for the foreseeable future along with the emulation for the OS (at least couple years). PS3 OS included numerous hidden features and hacks to support such emulation. There were even hardware features in the graphics chip for supporting such features.

From your point of view, This is not a thing because it is work, and as stated is pointless to do, also requires hardware which is not a target of RPCS3. and As initially stated the Emulation side is supposed to be for debug, however I can see this becoming more of a game player than a debugger in the future based on public wants.

From my point of view, It is not a viable option to make this emulate full roms and certainly not PS2/PS1 and hardware emulation, This requires too much time, and hardware. SA-CD is dead anyways IMO and if you wanted to read or write SA-CD then look into getting a drive that reads them and then using IMGBURN. It is not an emulators job to write disks, only read, and even so thats not required as most use ISOs and in this case Packaged games downloaded from PSN.