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
Get one of these bad boys:
https://www.aliexpress.com/item/1005004299310687.html
Can be used on multiple platforms and will neve drift due to hall effect sensors.
They are on Amazon for faster shipping but I get the feeling you’d rather save the $20. I think they are at Target too but ymmv.