My idea:
NX would be a storefront not a hardware.
Initially released for PC, with the possibility of cutting deals with Sony, MS, Apple, Google, etc, to make the store availiable for other devices (Nintendo could leverage their weight to reduce the percentage they'd have to give up or get a cut of the third party games sold within their storefront).
The end goal would be to eventually have as many Nintendo games availiable for it as possible. Automatic crossbuy for all games, if you bought it and your device has it you can play it.
Monthly subscription to have access to their entire catalog from past generations.
New Zelda would be availiable on day one. Mario, Slatoon, Mario Kart, Smash, etc would be released for it as well.
New Metroid, Pokemon Magenta\Cyan (re-imagined Pokemon franchise with AAA budget), Fire Emblem 3DS Collection (Remasters) announced during the NX reveal.
All digital, but you can still buy physical releases and special editions (you get a code with it, that ties it to your account, like on PC).
Nintendo branded line of machines could still be a possibility, but it would essentially be their version of SteamOs.