Look how expensive the PS3 was at launch, that exactly proves my point as only launch model PS3s have PS2 hardware in them as Sony dropped the approach to help cut costs, in the UK PS3 was £425, the Wii U CPU can't just be thrown in to help with new games either because it is old hardware conceived in 2010 it would become a hinderance in 2017 and beyond because it's not tailored to deal with more modern tasks. The programming for it would be problematic as well as it was designed for a different ecosystem, software emulation would be a better option and cut hardware costs.

BC is not a selling point of a platform it's just a complimentary feature and always has been as people don't intend to buy new consoles to play games of a previous console this is why PS4 isn't that phased not having it, only games that would be a priority to port would be the ones I mentioned as they have active communities that will be more of a benefit to help migrate. Other than that NX differentiating itself from the Wii brand won't be helped if the first wave of games are all Wii and Wii U ports considering NX is a departue from the brand, Wii and Wii U games aren't going to sell NX only ground up NX games will do that.

Finally yes the GPU being 3+ Flops is relelvant as it not only indicates high end costs so they can't afford to randomly throw in an extra CPU want if true but the type of GPU has an impact on what the CPU maybe handling during a game depending on its features, at that performance level the hardware could emulate Wii U with out the need of extra hardware thrown in. PS4 went for more high end costs but cut out the addition of BC components and sold at a slight loss to obtain its competitive price point and they're a bigger company mind you.

Your point about PS3 and price is so ridiculous it almost makes your post hard to take seriously, but regardless: 

-The PS3 cost was mostly Bluray and Cell, BC was minor.

-PS3 included both GPU and CPU of PS2 initially; they later removed the GPU to reduce costs. We're only talking about including the Wii U CPU here.

-Everyone owned a PS2; no one owned a Wii U.

-The idea here is that the Wii U CPU would be a functioning part of the NX CPU, not just there for BC. 

-If Nintendo is going to have a strong launch and perhaps introduce a paid subscription service, a key selling point is their back catalogue.  Wii U compatibility offers not only Wii U games, but everything from older systems already ported to the EShop and VC.  Starting from scratch (again) could be costly in both resources and time. NX needs a strong back catalogue download service from the get go to lure in old, lapsed Nintendo fans.

Your point about PS3 and price is so ridiculous it almost makes your post hard to take seriously, but regardless: 

-The PS3 cost was mostly Bluray and Cell, BC was minor.

-PS3 included both GPU and CPU of PS2 initially; they later removed the GPU to reduce costs. We're only talking about including the Wii U CPU here.

-Everyone owned a PS2; no one owned a Wii U.

-The idea here is that the Wii U CPU would be a functioning part of the NX CPU, not just there for BC. 

-If Nintendo is going to have a strong launch and perhaps introduce a paid subscription service, a key selling point is their back catalogue.  Wii U compatibility offers not only Wii U games, but everything from older systems already ported to the EShop and VC.  Starting from scratch (again) could be costly in both resources and time. NX needs a strong back catalogue download service from the get go to lure in old, lapsed Nintendo fans.

We have several conflicting NX rumors but one of the few things they all seem to agree on is that the platform is dropping discs in favor of cartridges. Without a disc drive, BC is a bit of a moot point. 

- Stop playing coy mate it's not a hard point to understand I don't get how you can't grasp the context of the point, you just admited Sony dropped the included hardware to cut costs, Nintendo going for the rumoured machine will be looking to cut as many costs as well to be economic and competitive so omitting hardware that's not required is a good place to start, a CPU still costs money dude and adds to the manufacturing cost.

- What exactly is the Wii U CPU going to be doing decorating the insides? It'll have no practical use in new games even games ported over from base model PS4s and X1s will be too much for it as it was never design to deal with tasks at that level. Outside of BC it will have no use and because BC could more than likely be emulated it would do nothing but drive up costs.

- eShop and VC will still be there plus how well did being able to play Wii games on Wii U help the platform in its launch year? Neither X1 or PS4 had a back catalogue and were fine starting from scratch, fact is BC is no longered a selling point and they will be in a far better spot focusing on getting ground up NX games out because that's what people look forward to in the long run, BC is for current Nintendo platform owners not non owners who they need to bring in. Zelda is the one exception and that's due to circumstance with it being a new release, if the rumours are true then there being a port of Smash further makes me believe BC with the Wii U won't be there or at least not at launch.

The CPU, as suggested, would add nothing to the cost, and would be similar to what Sony eventually reached.

Disc-based BC is gone, absolutely.  Downloadable BC will be a significant part of the system. 

Putting in hardware for BC wouldn't make sense without a disc drive. It would be a better to engineer a software emulation solution.