I think this could do OK ...
PowerVR GT7900 type GPU (or AMD equivalent), runs at full 800 GFLOPS when played at home (plugged in), automatically downclocks to 400-500 GFLOPS when played on the road.
4GB LPDDR4 RAM + 32-48MB eDRAM
New controller. Yes it's a portable, but it also has a new controller for home play. Possibly the controller can also be used on the fly.
Can wirelessly send a video signal to the television (the reverse of the Wii U)
6-inch LCD display (single screen)
Custom Nintendo OS, but runs a Android back end so Android apps can be ported very quickly, they can only be autorized by Nintendo, however, who gets a nice royalty fee surcharge on each download.
$249.99 MSRP. Same launch price as the Wii, except you're getting a home console and a portable all in one.
But I get the feeling Nintendo will go even cheaper on the GPU/RAM unfortuantely.