I thought about a potential NX home console and until now I just couldn't see an open market for it. The power market is set by the PS4 (and PC), the casual market by smartphones, etc. Even the XB1 is struggling to find an audience in between. The market seems cramped.
Now the one place that Nintendo still could go is low price. A 150$ Nintendo box, later down to 99$. The price is the gimmick.
4 ARM cores and a GPU by AMD, slightly above WiiU and below XB1. 4GB DDR3 RAM.
No optical drive, just download (maybe cards like 3DS). The WiiU remains the disc based option for some years.
Standard controller with Amiibo support but no screen.
Limited BC though the VC for well selling classics.
Most WiiU games get ported, eg Mario3D, Kart8, Splatoon, ZeldaU.