Please explain to me why it still is such a challenge to get an FPGA based board? These CPUs are used in more than used Amigas. They can be emulated in software. So I would expect it the instruction set can be re-translated into VHDL or whathever you need to design a FPGA image???
To me, just implementing the CPU in a FPGA seems a lot easier than a whole amiga in the case of a MiniMig/Mist/Arcade.