I wrote a very powerful industrial CNC control package on my A500 about 10 years ago. The whole project got cancelled though, and I don't know if I even have the code anymore. It did NOT control stepper motors, it controlled a common industrial interface board which in turn controlled analog and digital servo and spindle drives. Interestingly, the board plugged into an ISA slot, but just for power, like a KitchenSync. It had connectors on it for serial data. It was a perfect fit for an A2000!
Now, getting an Amiga to control stepper motors would be a real piece of cake! Especially via the parallel port. I have some hardware around here I could do this with if I really wanted to, which, frankly, I don't. Of course, owning a CNC vertical mill may have something to do with this.
There is no way you could connect a Toaster to the parallel port and video port. You would need to add a genuine video slot, by wiring directly to the custom chips, not just by plugging anything in.
I have considered lots of industrial uses for the MiniMig! Now, whether or not I ever bother with them.... The power of having a computer with Amiga capabilities on a chip!!