I tried out a version of the miniforce.cpp and commented out the CPU card and there were no angry fans due to angry scheduler. I'll try it a bit more and I guess I could implement something that just eats some cycles in the case you start without a CPU. I could easily use the HUD to slot in the CPU and then reset the machine and it started as it should.
MAME's core started out where it couldn't do a bare slot bus where one or more of the cards are bus masters. I don't *think* that's true anymore and you could now create a driver where all it does is host VME slots (or S-100 or whatever), but I haven't tried it either. I do suspect in the degenerate case where you run a bare slot bus with no cards and no CPUs the scheduler would still get angry.
While fiddling with this I found that the fccpu20.cpp default rom is for a Force 32 system as it is accessing a Force ISCSI board, same as for booting Besta, which wasn't around when the Miniforce was so I am going to add a force32.cpp as a chassi with another set of boards as default and maybe a generic driver/vme.cpp with a number of slots where all the loose VME boards could live until a proper system description is found/implemented for them.
Another thing also occured and that is I need a way to set the default rom from the chassi driver on the CPU board to support the system, eg the focus32.cpp have another rom configured on the fccpu20.cpp compared to miniforce.cpp They both boots PDOS but using different disk controller cards which is hard coded into the roms.