Right now Nintendo are massively missing out on the sales of the west, if they made a new console, targeted towards that audience from the beginning, that can also play all of the 3DS and Wii U games IMO that would make it a third pillar and really quite appealing to the masses IMO.
Nintendo should put their software at the forefront, the new platform should always be able to play everything that came before it, you buy the game and you can play it on any new Nintendo system.
The library of content on Wii U isn't too big to port it over to an X86 model, similar to how Microsoft lets you download a patch from select 360 games to play on XB1.
Wii U could probably brute force emulate 3DS games if Nintendo wrote an emulator for the purpose, so I doubt any significantly more powerful system would have issues.
Future games could all be made using the same API, PC can have scaled graphics, resolutions and gameplay features, if Nintendo targeted that same approach with their software then any hardware they release could run on anything and their older content could even be ported over to increase the size of the library.
Personally I hope Nintendo takes this kind of an approach.
The hardware almost shouldn't matter, so long as they make decent profits off of games, make a small profit on hardware and don't go crazy on releasing a new platform every year, rather play catch up with a new console to fit in with Sony and Microsoft, then release a new handheld when the tech can run a decent version of the new console's games and then everything can work on that handheld.
This could be Nintendo's competitive edge, they'd definitely appeal to the 3rd party publishers if they can get their audience to buy Nintendo again.
Developer output would be much greater if they only had to focus on a single API and treat all of Nintendo's hardware as a single platform.
You may say "well what would be the point in buying the next Nintendo box", well newer machines would be more capable, run the games better, in the case if a handheld it would allow you to play all of your Nintendo games on the move, you may want both the handheld and the home console to play it the best in all places and that would also allow Nintendo to target every market much more fluidly.
If families don't have as much money then they could just buy the cheaper Nintendo system, that still allows them to play all of Nintendo's games and Nintendo would end up selling way more software in the long run, so long as they can stop people pirating it, which could be where a proprietary memory card/cartridge for the games could be useful.
Games can be made on Cards and the system could still have a Bluray drive for those movies, if Nintendo are willing to pay for the license, if not then it would probably be just as capable of streaming content from services.
I really don't think the hardware matters all that much, Nintendo just needs to treat it as the vessel for people to access Nintendo's content.
I'd say the console should always, at least be able to play everything that came from this generation moving on and at some point in the generation a new handheld can do the same (but with some scaled down graphics, resolution, same frame rate for experience).
I think this is the most logical thing NX can be, without Nintendo stating exactly what it is.
