I have been thinking of either trying to get Doom to run whilst mining or even trying to get two instances of the miner OS on a single card to have them switch back and forth. Mostly a fun project with some old mining gear
What are you trying to doom? You mean you are trying to kill the miner while mining?
I think you can't able to boot sd card on the miner with dual OS but I think its fine just boot the braiins in SD card then move jp4 to original position to automatically switch to stock firmware.
Or you can use bos toolbox because its allowed to install and uninstall os through bos toolbox.