I don't know that they need to create more studios. However, I DO think they need to get back to making their own goddamn franchises themselves, in house. It has bothered me in general that it has become a growing practice for Japanese studios to hand off their properties to other developers, especially Western developers, to make new games for.
I don't think there's much denying that when it comes to the BEST entries in Nintendo's main franchises (excluding ones that were always made by outside studios like Fire Emblem, Smash Bros. and Kirby), they have always been made by Nintendo, in house. Whether it's Mario, Zelda, Metroid, F-Zero, Wave Race, whatever. They used to develop most of their big franchises themselves. They've moved away from that, and I would really like to see them PERSONALLY develop a new 2D Metroid, a new proper Star Fox, a new F-Zero, a new Wave Race, etc.