So, based on this, I'll be giving my input here.
The NX definitely can't be another home console, neither can it be a power home console meant to compete in firepower against PlayStation nor Xbox. No, the home console market already has these 2 giants playing catch up with each other power-wise. Another home console on the market would be bad news for everyone involved.
What Nintendo needs to do is drop both Wii U and 3DS, stay away from their competition while also reaping profits off it, the handheld market is dominated by Nintendo at the moment, MS doesn't have interest on it, and Sony dropped it along with the Vita. Both MS and Sony are focusing on the home console market by making stronger consoles every single time. The NX could, instead, be a handheld with slightly higher power than the Wii U (the Tegra X1 rumors give ground for this, and it is technologically superior, being based on the ARM architecture) which is still very powerful for a handheld. If it can connect to TV, it could work as a handheld without abandoning a home console-like experience (TV play, local, single console multiplayer) while also being a cheaper option than Sony and MS's offerings.
Luring in third-parties (while financing potentially critical successes, if not commercial ones a la Bayonetta 2) and focusing their own software into a single plataform. Thus generating lots of exclusives.
Tl;dr. The NX being a powerful, modern handheld with TV connection, for a lower price and with lots of exclusives would serve as the perfect alternative choice in gaming, thus being a viable purchase even if others already have a gaming PC/home console. I could see it selling amazingly well, myself.