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
The unfortunate thing for your desires is that portability is the reason the Switch has been so successful, and is also the reason it doesn’t have “modern” specs. I’m sure the next system will be much more powerful, but I’m also sure it won’t even be near the power of the PS5 or XSX because I am 100% sure it will still be a console that can be played on the go.
Thankfully as home consoles have much more transparently become purpose-built PCs using variations on off the shelf hardware, ratcheting down graphics to function on a lower power system isn’t nearly as hard as it used to be.