I believe, from his comments, that MikeJs board design is made to be able to emulate multiple platforms, either by using other cpus on daughter boards or everything in the onboard FPGA.
This means that, to answer your example: You could put a 68020 on a daughter board AND if you had an FPGA implementation of the AGA chipset that you could put into the onboard FPGA, then yes you could use it to emulate an A1200.
MikeJs earlier post was saying that because the FPGA he has used is much larger than the one in the MiniMig (3x larger!) it should be able to fit both the MiniMig OCS chipset and TobiFlexs tg68k into the FPGA together so this could become a good board for MiniMig projects.
However he's designed it so that it could be used for the implementation and emulation of many other systems.
That clarify?
Andy