A Transparent Wishbone-to-SPI Bridge Supporting Execute-in-Place (XIP)

This allows you the possibility of booting directly out of the SPI, where you put a first-stage bootloader that copies the rest of the system into RAM.

Lots of systems do this already by means of mask ROM bootloaders; some people might not want a fixed payload provided by someone else to be the first thing that executes. On the other hand, executing out of SPI is very interceptable.