100% agree with this!!!
Bone shaker’s isn’t a bad idea! My game, Festive Fight, could use the link cable, too. Right now, 2-player mode is just sharing the one Arduboy between two people, sharing the buttons.
I’m also wondering what asymmetric features that we could offer. For instance, on the Nintendo DS, there were some features where you could plug a Gameboy Advance game into the bottom slot and a DS game in the top slot to transfer all sorts of data one way or the other. Pokemon let you transfer your creatures from the GBA game to the DS. Also, the Wii U had asymmetric gameplay in a lot of multi-player games considering that it only had 1 single screen.
Another note, there was a Gameboy game that could support 16-player multiplayer. It was a clunky FPS, but I wonder if there was a simple technique they used to daisychain Gameboys that the Arduboy could do using this link cable method.
(Video of 2 people playing)