However, according to rumour the CD32 ROMs are not the full 3.1, but a slightly older version.
It is indeed an older version. I would be very surprised if they contained A1200 IDE and PCMCIA support, and even WriteChunkyPixels() may fail due to lack of Akiko. Even the A1200 and A4000 3.1 ROMs are slightly different from each other so I doubt the CD32 version would work - at least not without missing or incomplete hardware support.
Chris