I strongly dislike the idea, for a fixed/home console an accelerator does not make much sense, for a handheld... well I toyed with the idea in the past and ultimately I think it is a bad idea. On the handheld side you will always face many constraints some that could be alleviated by an external accelerator some that can't. Actually the only thing that can get conveniently altered by an external device is GPU "power". Increased GPU "power" won't get you better assets and assets weight has to be kept low on a handheld device, there are hardware reason and business reason for that matter of fact: handheld can't sustain the type of AAA games we see on PC and home consoles.
One could think of complicated extension scheme, with date that would need to be saved on the accelerator, etc but it is complicated and it increase the cost of the accelerators as all of sudden it needs storages a way to deal with it, etc. It is a lot more complicated than plugging a GPU through USB in a laptop which already on its own provides a lot more computing power than a handheld device, that has storage in spare, etc. and cost more than a home console...
There is the matter of control, a handheld offers more options for control than a simple controller ever will, and that include functionality that might require the player to look at the screen and interact with it. How are you going to deal with those situation when the gameplay is cast from the handheld to the TV?
Overall I scared that Nintendo did only half the job here, looking at the game they are producing and their view of gaming and their market shares handheld is better place for them to be, I suspect they know it but they did not dare to push the logic to its end, aka if the handheld is primary device then one needs to put a good amount of thoughts on how the tv or a secondary screen can blend in. Actually a secondary screen is non necessary and can in fact be an hinderance. I'm scared Nintendo went through a lot of hoops to achieve something unnecessary aka some reverse casting which is usually done from the more powerful device to lesser one.
Even if they technically achieve it the resulting device will never be a proper home console as the handheld will dictate the gameplay, take attention away from the tv often, etc..
As I said in this thread or in the other Nintendo thread, at this point the best business plan for Nintendo is to go with handheld only or I could say handheld foremost. They should push out a cheap, robust handheld out. I will point again at Amazon and its late Fire 7 as a reference point, cheap product is a no brainer for lots of customers, I will get one from my parents in laws as I was out of idea for a gift. Subsidizing and aggressive temporary rebates have a greater effect too as they get to prices where we can speak of real impulse buys. Now it would take quite a change at Nintendo headquarter as the 2DS goes on showing that they are unwilling to do any effort to get devices into costumers hands. This fall my wife suggested the 2DS more than a couple times for me as a present and I refused as for me first it is not worse the price and 2 it did not get updated as the main line 3DS... It is by the way a sign that things are not changing at all at Nintendo HQ.
For the TV side of thing I think they need more of an aggregator with some will of its own han an accelerator to leverage the huge secondary screen space a tv offers in local MP oriented games. I posted on the matter already.
If the rumors are somehow right my belief is that Nintendo will end with something quite awkward as not matter how the idea is implemented, the whole approach is conceptually flawn
