NPD: 3DS Sales Lowest Since July 2011. About to Fall Behind PSP.

[Soundwave]

It depends I guess Nintendo could get a GPU like the PowerVR 6430 (this is the same chip in the iPad mini retina) for dirt cheap. Throw the 3DS GPU in there (even cheaper) + a ARM Cortex A9 and you have probably a very cheap setup that can run all DS/3DS/VC games and all Android stuff too. 

It's not so much the chipset that makes things expensive, it's the LCD display, battery, and any type of custom component (like say a 3D screen) that will drive your costs up. If you stick to widely highly mass produced parts that are more than a tech cycle old you can get components for cheap. 

To be honest, I have to wonder if your basic idea might not be a better play than the "New 3DS followed by a Fusion platform circa 2016" roadmap. Nintendo is absorbing huge losses on the portable battlefield, waiting for 2016 to send in the cavalry probably only allows more damage to be done. 

A tablet that could play hundreds of DS, 3DS, NES, SNES, N64, Genesis, TG16 games on top of Android games and have enough grunt power to draw Wii games in 1280x720 resolution with fancier lighting effects ... I dunno. Maybe waiting for 2016 is too long. Nintendo could release a pretty kick ass handheld for cheap next year if they really wanted to. 

I`ll trust you for the tech stuff, because i really have no clue about that! :D
I guess a 3D screen wouldn`t be needed. Nintendo would be the first to say it wouldn`t be good for kids and then it would be 3DS all over again.
And of course, Nintendo could get other consoles for the tablet VC, if you will.

It`s not just a question of going this way or that way. Fusion strategy or tablet strategy.
I believe there`s a market for both things. Not to mention that in terms of games, Nintendo would take a step back in terms of what HW would allow them to do or how big could their games get. As far as i know, tablets don`t really have GBs and GBs of space to handle several games. Consoles can handle it because you can get the games in a store or have a external disk next to your console.

In terms of timing... i really don´t have a good idea on what the best time, but releasing every piece of hardware at the same time (specially the consoles) would be a way to push people to adopt more than one or at least, even in regards to marketing, would be best to show the exosystem right at the start.

This is basically what I came up with on a cost basis ...

Nintendo Budget Tablet (Nintendo Touch)

- 3DS GPU + ARM Cortex 9 (dual core) CPU + PowerVR G6430, basically a 3DS + an iPhone 5s chip customized for gaming performance. 1.5GB RAM. 

- 6.3 inch LCD, 1280x720 single screen, no 3D. Not the greatest screen quality but far better than the Wii U controller or 3DS screens. 

- Runs custom version of Android per Nintendo's specs. Main menu has Miiverse plaza when you boot it up. Nintendo controls which Android games are allowed and also charges a Nintendo "tax" on games so they get their cut of the action. So $2.49 for the standard Android game, maybe $9.99 for things like Minecraft and Final Fantasy III. Nintendo pockets money on each download. Facebook, Instagram, Google Maps, WhatsApp, Twitter, Netflix, Hulu, Youtube, and many more apps can all be free however. 

- Full Virtual Console support (NES-N64, GB-GBA, DS) and also 3DS support. Requires a control cradle to play games in vertical (DS/3DS) mode, but many 3DS/DS games could be reworked quickly to be able to play in horizontal mode. $2 for NES games, $4 for SNES, $6 for N64, $15-$25 for DS, $25-35 for 3DS. 

- Ships with "Nintendo Learn" software. Basically a mashup of Brain Training, Art Academy, and Louvre Museum. Point of this is to make it seem like more of an "edutainment" tablet that kids can sucker their parents into buying (way cheaper than a iPad too), lol. 

- Price: $179.99, spring 2015 launch Japan, summer 2015 NA/EU. 

That's actually pretty powerful too, a good deal past the Vita. It would be able to run something like Xenoblade in HD without much fuss.