would you have done just a straight clone or would you improve the visual output in some way? what sorts of things could you do while retaining pinout compatibility?
HDMI output would have been the main display improvement but given where a PPU or a VDP sits in these architectures, you could do a lot of fun stuff including running your own CPU core on the FPGA. (Edited - thought there was a wait pin from the PPU to the CPU but looks like it's an interrupt)