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
Backwards compatability. Getting the 3DS has really made me appreciate how many games I can play on the system since I can play 3DS/DS/GBA games all natively. Whatever Nintendo does with the Switch 2, it should be backwards compatible with the Switch so that I can continue playing my favorite Switch games without having to wait for a port.