For me, some DS games would be much better experiences on a large screen, and it's not unprecedented for Nintendo to make devices like this. Each of their consoles since the SNES has had an add-on that allowed you to play its' current handheld on your TV.
-Game Boy Player on the SNES
-Transfer Pak on N64
-GBA Player for Gamecube
I realize it would be difficult to properly emulate the games on the TV due to the touch screen and dual screens. Well, Final Fantasy: Echoes of Time (which emphasizes cross-platform play) simply has both screens take up a portion of the TV screen. As for the controls, it's simple:
-A, B, X, and Y are replaced by the D-Pad on the Wiimote
-The DS D-pad is replaced by the analog stick
-The shoulder buttons are replaced by the Z and B triggers.
-Touch-screen would be handled by pointing at the appropriate area and pressing A to 'tap', or holding A to draw.
-Games that use the mic could be handled via WiiSpeak
I don't see what would be so hard about doing this, especially as they could simply allow you to use the DS as a controller if necessary.
