Foppe posted... From a technical point of view, yes.
But it wouldnt be practical.
Going the dock way might or might not work depending on if and how Nintendo blocked data from being transfered from it into the console. The USB speed will be a bottle neck.
...on the other hand, nothing really prevents the dock from being the more powerful CPU/GPU and the Switch is the addon CPU, but that would be pricy.
Adding one on the cartridge is still possible. It will however end with a really strange and heavy card. Best solution is probably a twice as tall card that ends with a cabel that goes to a box with the extra processing power and more RAM.
Which most likely will need an extern power source.
Add a card reader and you got an addon like the 32x.
Could just sell an upgraded dock as a separate peripheral to allow that choice. It'd probably sell well enough.