In terms of hardware, I find the Vita to be a better-designed game machine than the later two systems.
It has better specs than 3DS and it's screen resolution is higher than that of the WiiU.
It's a fully portable system, it uses cartridges and it's features actually seem appealing rather than gimmicky, if used right.
It also costs considerably less than the WiiU and only slightly more than a 3DS.
It's also combatible with the PS3 and has a sleek design.
The only thing missing is TV output and the analog sticks could be a little bigger.
I think the system would sell much better if it got it's price reduces and if it got more "killer-apps". (why are there still no exclusive Gran Turismo, MGS, GTA and God of War games on Vita?)
It's basically the portable system that eliminates the need for a home console, in some regards.
And that is what I think the platform Nintendo would need is.