You're missing the point. Retrogaming is about creating the familiar feeling of playing the games. A WiiU controller is not the same as a NES controller. HDMI is not the same as CRT + Scanlines.
Retro gamers generally play on the original hardware with CRT screens. If they can't do that, they play on emulators with using controller input converters and shaders or scanline generators. Gaming on a WiiU does not recreate that experience.
I absolutely agree that retro gaming is about the "retro" feel, but I don't see how you can have that and have an internet store for legal roms. Would a raspberry Pi with an authentic NES controller + CRT screen connected through composite input fulfill your retro requirements for example?
So does having a TCP/IP stack and a download store :)