Hey Sarainia! I actually do this kind of thing during my day job as an AI researcher. I recently open-sourced a little Unity example of a system that generates very simple two-player games: https://github.com/possibilityspace/bluecap and I made a video to go along with it (although it's very long and includes a load of other, unrelated things you can skip:
We've had a few PROCJAM entries in the past that randomised rules too - there's one about using cards to influence the outcome of a battle between two AIs, I forget the name of it now though...