Lets talk about 2 display systems where the 2 screens have differant data going to them.
I am talking about the Nintendo VS. System or Tysons Punch-Out.
Since we already run super-resolutions to enable 240p over the hdmi port into a hdmi-rgb convertor , it should be doable to use a 1x2 video wall processor in between to split the hdmi super-resolution into 2 normal resolution screens that are encoded as player 1 screen and player 2 screen.
I dont know if the Mister has the horsepower to actually run as a VS system or even Punch-Out but it does seem this may be a path to enable the video portion.
The video wall processors have gotten very reasonable and can be picked up for $100 , add 2 hdmi-rgb convertors for crt's or just run 2 lcds.