Actually my idea for a Nintendo Handheld isn't handhelds at all. Be it a Playstation, a Wii, an XBox, a GameBoy, a PSP, and so-on and so-on, all those devices are computers with varying degrees of capabilities.
3DS at it's core is a computer, and computers are versatile. You don't need a Nintendo to run a Nintendo game. A PC can emulate Wii games with proper coding and trial and error, and a PS3 can emulate a SNES game. Once the hardware is capable of an emulated Nintendo game, the hardware stops mattering, and the only thing that makes a Nintendo game truly feel like a Nintendo game is the method of Input (controller).
Using a Laptop, plugged into the TV, with a USB adapter for a GameCube gamepad, I was able to enjoy several Gamecube games, and it almost felt like the genuine thing. When emulating at proper speeds, compatibilities, and using proper or similar to original input methods, the line between Nintendo system and other computing devices blur. So my WISH for Nintendo, is to stop developing actual systems, and instead focus on only making gamepads for PC and Mobile, and setup an encryption that only allows Nintendo games developed for PC and Mobile, to be only playable by connected PC and Mobile designed gamepads, MUCH like how Portal and Half Life 2 on Android are exclusive to Nvidia Shield because of Input issues the Shield is able to solve (Ignore Side-loading on Tegra 4 for this arguement). I think this way Nintendo can still develop Nintendo games, for Nintendo fans, and control that "Nintendo Experience" while at the same time not having to deal with system research, development, and production, and not having to worry about the sales o those devices.
Nintendo have stated that they don't want to put Nintendo franchises on Mobile because they think the touchscreen isn't an acceptable enough input method for their types of games, and while I agree that Mario, or Kirby will never be acceptable with touch controls, I know for a fact that bluetooth controllers are AWESOME at remedying that situation. Gaming on emulators with my Moga has been very satisfying. A proper input device makes a load of difference when gaming on an Android device. So I'd like Nintendo to supplement Wii U's and 3DS' successor console and handheld with PC and Mobile, and add the twist that their games be only playable in the case of having a Nintendo design and patented gamepad.
Also some of those touch-only NDS games feel right at home on Android/iOS. I've been playing The World Ends with You lately on Android and I honestly feel it superior to the NDS version. Also playing Super Metroid on my Moga, Okamiden on my Moga, Order of Ecclesia, Tactics Advance 2 just by Touch Screen, New Super Mario Bros with a Moga... Honestly... Just replace Moga with Nintendo-designed Handheld and you'll be golden.
If you really think about it, the actual Wii U or Wii sstem is irrelevent to how you play that system, its all in the control. The same idea that at their core, the PS3 and X360 are the same fucking thing as well.