Why? Just leave it in the dock.
To sell a package without the dock might be practical for many people, but to make a special non-portable version doesn't seem necessary at all. This is Nintendo we're talking about; do you really think they'd charge less money for it anyway?
I've never seen anyone refer to the PSP as a failure. It never hit DS levels of popularity, but it had its own devoted market.
I think the peak of 3DS' popularity was around when Animal Crossing: New Leaf came out. I've gone to New York Comic-Con every year for the last 5+ years. When AC was under 2 years old, my StreetPasses filled almost instantly there. This year (earlier this month), it took over an hour to accumulate 10 tags at one point, and that was with literally tens of thousands of people there.
There may still be a market for dedicated portable gaming, but it's a lot smaller than it used to be. Of course, this may change if a great new device releases. When the 3DS and Vita came out, they were far more advanced than the phones on the market at the time. But the smartphones of today have leapfrogged both dedicated devices.
But ever since the reality show boom, most TV channels don't even show Wii Ones any more.
::runs::