I would recommend a similar approach on starting to get on route to an A1200 level of a MiniMig 2.0 by use of a larger FPGA, SDRAM, and an external 68020 CPU (need CBT level shifters) since it is going to take some work to get that really nice soft VHDL 68K core upgraded to 68020 level (Icache, pipline etc ...) and to get AGA graphics.
:-)