I love these retro cores which extend "what might have been" from the past into the future. Another impressive example is the Apollo FPGA core which over the past decade has faithfully built on the Motorola 68000 series to extend beyond the last chip (68060) adding a variety of modern CPU affordances like 64-bit, instruction fusing/bonding, super scalar, out of order execution for CPU/FPU, dynamic branch prediction, etc. There's an add-in accelerator board that replaces the CPU in an Amiga and the team is working on now adding Atari ST emulation/acceleration to the core.