I would like Nintendo to use/adapt "Modules."
Modules could be a add-on through USB who lets you plays retro consoles.
Let me explain:
The new Nintendo console will not have backwards compatibility, however, if you want to, you can buy a Module for (50-80 dollars) connect it to your NX and then you can play your old games. Be it Wii, WiiU or Gamecube.
a) Gamecube Module = 50USD. let's you play all gamecube games that you own through discs.
b) Wii Module = 80USD. Let's you play all wii games that you own through discs.
c) WiiU Module = 100USD. Let's you play all WiiU Games that you own through discs.
You can also download them, but then, they will not be compatible with your modules.
Could also work for retro consoles, but instead of old cartridges, they can use SD Cards.
This would make people who own physical happy, while those who wants digital just can download them.