It doesn't have to be complicated. Think MS Surface Book. Motherboard, CPU and small battery in the detachable screen. Plug into the base and you get more battery and dedicated GPU.

If I run games on the tablet I get a certain level of performance, if I run in laptop mode I get more.

This could readily be applied to a console. There would be enough hardware in the screen to run at a resolution and frame rate appropriate for the screen and power envelope. With access to a bigger GPU, more RAM? and fixed power supply in the base, you get a higher frame rate, resolution and perhaps improved effects. Games are developed for the full spec machine and scaled down for the handheld hardware.

AMD could actually petition Qualcom for Adreno. - Remember, Adreno is derived from AMD's tech, and if you reassmble the word "Adreno" it spells out "Radeon"... It's not like AMD doesn't have experience in Ultra-low powered cores.

AMD has 28nm APU's today, quad-core Puma+ and 128 GCN shaders running at 2.8 - 4.5w of power, perfect for a tablet sized handheld... Keep in mind Polaris/14nm tech is roughly 2.5x more efficient than the older 28nm designs.
So having a 320-512 shader design wouldn't be far-fetched, it would certainly give Tegra a run for it's money.

As for Thunderbolt. Yuck. Why would you bother when Tegra has PCI-E lanes at it's disposal?
1080P rendering on Tegra isn't going to happen. Even with two chips working in Tandem with a degree of graphics quality we have come to expect this gen... There are multiple reasons for this, but I don't see the need to get into it again.

I originally suspected Polaris, but correct me if I'm wrong here...Polaris is a GPU iteration, and not a System on a Chip solution. There's also reports of the newer Polaris tech sucking more power from the PCI-E lanes than the standard calls for, so I don't think that would work in a portable system.

If I recall, Adreno is fully owned by Qualcomm now. They bought the Imageon series from AMD, so the idea of using it would be just as feasible as Nintendo dealing with nVidia. Both require dealing with another external company.

Does Tegra have some kind of PCI-E passthru that I'm not aware of? Also, that kind of architecture could just swamp the existing bus if both devices share lanes. Remember, the idea is to pair GPUs from different physical devices dynamically, which is exactly what Intel Thunderbolt was designed for. From a hardware engineering perspective, why hack together a solution when there's an already established one?

It's been awhile since I've seen AMD's low power SoC designs, but if there is a proper, analogous answer to Tegra, I'd suspect that it would be the one Nintendo would be aiming to use.

You are correct. Polaris is a GPU solution. It can be paired up with any CPU Core/Logic that AMD desires. Such as... I dunno. Carizzo/Puma/Jaguar/Excavator etc'.

Polaris and PCI-E are two fundamentally different things.
Polaris based GPU would not be drawing energy from any PCI-E lanes if it was in an APU.

I did iterate on that.
AMD can petition to get Adreno technology and incorporate it into it's SoC designs. AMD has dealt with ARM/3rd party logic/chipsets before.
Intel did it all the time using PowerVR graphics solutions in various chips rather than it's own I.P.

AMD isn't scared to use other vendors technology... But more often than not, they also don't need to... And they would likely be more than happy to do it on Nintendo's behalf considering how much cash is dangling in front of them.

Yes.

4x PCI-E lanes is more than ample for mobile-based-socs to be paired together in a "Crossfire/SLI" approach.

PCI-E can technically do everything Thunderbolt does with a few tricks. Tegra has native support for PCI-E and not Thunderbolt, from a hardware engineering perspective... Going with PCI-E would be cheaper, faster as the work has already been done.

AMD does have low-powered SoC designs even today, usually based on it's low powered Cat cores and up-to 128 Radeon GCN shaders... Keep in mind though that AMD isn't targeting phones... More like low powered Laptops and Tablets.
Graphics Core Next 4.0 and Zen should hopefully be the successor to the current Graphics Core Next 1.2/3.0 and Puma.

I don't understand your disgust for Tegra when it's practically the perfect use case for Nintendo since their very power consumption limited in small form factor scenarios and Nvidia has a good recent engineering trackrecord for pushing high perf/watt efficiency ...

AMD hardly even competes in ultra low powered devices and heck, ARM (these guys also design GPUs too) or Qualcomm would make far more sense than AMD ... 

x86 doesn't make much sense either when it's got a noticeable instruction decoder logic overhead that sucks up quite a bit of juice and I know AMD has an ARM license but I doubt the end results will be even as good as the dedicated ARM microarchitecture designers are like those from ARM, Apple, or Qualcomm ...

Great, that's all I needed to know!

We need a new leak to discuss.

Things are boring on VGC without them...

It's not that I don't like Tegra. It's that I don't want Tegra in a console. :P
We already had Tegra with the Ouya.

If Nintendo goes Tegra, then chances are they will miss out on allot of ports and that will turn me off completely from Nintendo's next console.
The Wii U has proven that tons of exclusives do not always shift hardware.

Still, if they can pull it off, all the power to Nintendo... But there is a reason why I haven't owned a Nintendo console in multiple generations.

With that said... ARM is preferable over PowerPC from a support standpoint, Android has pretty mature API's and hardware support these days, all things considered and has a massive casual-based audience with games to suit.

But why don't you want Tegra in a console ? 

You're probably right that they'll miss out on a lot of games shared by the HD twin and PC since it won't have enough compute power or bandwidth to run most of them at an HD resolution but that's just the reality that we have to deal with mobile chips ... 

The WII U did not but the WII DID ...  

Well, at least Nintendo gets conservative rasterization and raster ordered views but I would've preferred if they went to Intel for GPUs since it has even more interesting hardware features like updating tiled resource mappings via GPU commands and programmable blending ... 

Sounds really expensive where you might end up with stuff you don't need if i think of practically using it:

1) as a home console, the controllers it comes with might not be good enough as they are designed to be used as a hand held. Meaning I'll have to buy a controller and a docking station.

2) as a handheld, you'll need a charger set, carry case and it will most likely be bigger than a 3DS and possibly a Vita, meaning it might not be easy to carry around in your pocket.

I don't think it's complicated, but i do think for Nintendo to get this right, they will need to sell 2 bundles, one for hone gaming and one for portable. The home edition will come with a proper docking station and a proper joypad and the mobile one with a case and charger set. This way they can market is easier as well and costomers won't need to pay for this they don't need.