This is a weird one, but I’d love to see a reimplementation of the sensor bar. The gyro controls haven’t cut it for me. I like how the Wii U game pad had the sensor bar built in to the bezel. The real engineering nightmare would be squeezing IR cameras into the top of the Joycon
They did a good job with Wii U’s latency. The only thing that was shit was its range, which wouldn’t be a big deal because you’d only want to stream to the TV if you were in the same room as it. Ideally it’d be a dock that you can physically put the console in or stream to it.