How about USB PCs I know Black Friday/Cyber monday is nearby. Its 2020 I'm pretty sure there has to be a $125 that will be on sale for $100 or less usb pc capable of running this. You hook 4 of these on those 4 way monitor and with a KM usb sync there u go and you could stack this.

The idea behind this is to make a 5 or more box hardware multibox available at a reasonable/affordable price.
Kinda #MakeMultiboxingGreatAgain lol