it's questionable how many developers will go to the effort of creating games that make use of the extra horsepower when docked, rather than simply opting to program for the slower overall GPU clock speed
This. A thousand times this. No developer in their right mind is going to program a game that doesn't run properly on the portable. The downscaling of the portable is just too profound. 40% clocks? So the console will suffer from portablitis (similar to how PC games suffer consolitis).
If they then kill the portable line (currently 3DS) in preference to Switch, they may well kill both their portable and console markets with one stone. I know they have a NIH ("Not Invented Here") culture, and this has resulted in some excellent and novel gaming (thinking Wii here), but this new console seems strategically unsound.