I’m sort of surprised not to see this game in the suggestions already!
Planet X3 is the game by David Murray, also known as the 8-Bit Guy on Youtube. It’s an RTS that will run on a toaster powered by a potato.
I think it would be cool to do an episode on a brand new homebrew DOS game like this.
Another option would be retro city rampage (which I think has been mentioned on the podcast a few times), but I like the look of this one better.