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.