I like and support your idea - that'd actually be cool. Players would be able to not just create levels, but whole cohesive level packs with some form of a goal beyond just "going right". I think it's an excellent idea.
Beyond the fact that I think you're wrong, meaning the "twins" have enough defining features of their own (Touchpad, SIXAXIS and PSEye versus Kinect 2.0 and robust media functionality provided by the HDMI In, the TV add-on etc.) and they're certainly not "stripped-down PC's" any more than the N64 was a stripped down SGI Indy, the SNES was a stripped-down Apple IIGS or the Xbox 360 was a pair of PowerMac G5's stuck together with duct tape etc., seeing that they're based on customized CPU/GPU/Memory designs used exclusively in them (there are no octocore Jaguar CPU's on the market nor are there any PC's equipped with GDDR5 memory as RAM, or memory shared in a HSA scheme for that matter) just like any other console before them (technology does not live in a vacuum - every single chip used in a console is derrivative from the general pool of computing), I disagree completely with the premise of your argument.
A video game console is unlike any other "toy" - toys have to be unique from the outset since what you see is what you get. A console's primary purpose is to support video games, unique solutions for the plastic you play the games on come second. The Wii has shifted the focus of console gaming from the games onto the gimmicks and I hate that. Some of the best video game consoles of all time had zero gimmicks out of the box and nobody batted an eye, why? Because they played video games and they did it well. All they had to do was be efficient at their intended purpose, be equipped hardware that will remain relevant and supported throughout their lifecycle. If you're building a console on technology that's obsolete Day 0 and the support dries up before you even get a foothold, especially when you had a headstart of a year, you know mistakes were made at the design stage - that's the harsh reality of it all. The second screen is neat, but you know what's neater? Having games to play.
From a gimmicks perspective there was nothing differentiating the SNES from the Mega Drive/Genesis - they were boxes you put cartridges in and they came with gamepads - shocking development. Despite that, they both have amazing libraries of exclusives and a hefty library of cross-platform games to boot. I can totally imagine the great majority of Wii U games working perfectly fine without the gamepad because I'm familiar with the concept of pop-up windows and menus - the chief example of that is ZombiU, now re-branded and re-released as Zombi. Nobody could even imagine this game working on anything other than the Wii U and yet here it is, re-released with improved graphics on PS4, Xbox One and PC. Admittedly a cash grab title, but it demonstrates that the gamepad, although neat, is completely optional 99% of the time.
Anywho, the tl;dr version of what I'm saying is that I don't think the Wii U has any more right to be on the market than the PS4 and the Xbox One just because it's "different" - different doesn't mean better. Sometimes you can be innovative to your own detriment, and the Wii U is a great example of that in motion. That's not to say that I don't like innovation, it's all nice and dandy, but it's a gamble - sometimes it pays off, like in the case of the DS, sometimes it doesn't, like in the case of the Wii U. I think Nintendo tried to copy-paste the DS experience into the home console market and failed for very obvious reasons - while on the DS the screens are separated by about 1 cm and constantly in plain view, in a home console environment you have to actively look away from the TV if you want to see the gamepad, so your immersion is immediately broken and you're prone to screw up since you can't see what's going on. That, and the gamepad increased manufacturing costs by a huge margin which led to a hefty entry price point for hardware that was ultimately obsolete and deserved retirement before it even left the assembly line. I mean, PPC7xx? Really? C'mon. It was fine on the GC, it was funny when you stuffed it into the Wii, but in the Wii U? The console that was supposed to be Nintendo's comeback to the mainstream audience? Well that panned out great.