That's the greatness of this theory. They don't have to develop 2 Smash games, only one scalable. The same team, once Smash in finished, can move to a new project. For example, NX can have A Link Between Worlds, Triforce Heroes, Hyrule Warrios and Zelda HD, without the need to develop the remakes to fill the gaps, and anyone will be able to play in any of the Nintendo NX devices.

All of the teams developing for a single OS will be better and will solve part of the HD problems. The only thing that could make it harder than the Wii U, is a harder architecture, but there are some hints that NX could be similar to Wii U, so less problem.

They had problems with Wii U because that was their fist HD console, they were first time making games in HD after few generations of making games in SD. Whole this unifying plan is because of speed of developing and supporting two totally different platforms, 3DS and Wii U showed that they efectly support two completely different platforms, but with unifying platform they can make one game in same time for two consoles, in that way they will have much effective support.

Saying that, NX will have Wii U BC suport or Nintendo will simply port most of Wii U games for NX.

They expanded a few teams and merged a the handheld and software division, but that was made shortly after the Wii U. The result of those expansions will be seen with the NX. But the thing is, Japanese investors seem to be greedy and cheapskate, or at least Nintendo's investors are. Sony is more like a Western company in the sense they will bleed money just to keep market share and Microsoft uses the Xbox to gain mindshare for Microsoft rather than profit with it.

We're talking about BILLIONS here. Expanding a few teams, changing a building, and  give a share of the profit to investors doesn't cover it