Just a random thought on the IIsi. Since most of us have amounts of memory that would have seemed crazy at the time these machines were introduced, the 1MB of onboard RAM isn't particularly significant. It also has the performance penalty of shared RBV access. The RBV interleaves memory access on Bank A on both the IIsi and the IIci. Losing bank A on a IIci would be unfortunate, but losing the soldered 1MB bank A of the IIsi probably wouldn't be missed.

I'm aware that there's a tool out there that makes a 1MB RAM disk to consume the 1MB of onboard RAM to make sure none of your regularly accessed RAM overlaps with RBV access. But I was toying with the idea of just making that 1MB disappear in ROM. It would still be used by RBV, but just to remove it from use by the memory manager.