Pretty much agree with your entire post and I wholeheartedly agree with the bolded.  While many forum-goers aren't all that hyped for Mario Maker, it really does have the most potential to appeal to a lot of people, especially the broader market.  Aunt Kathy that's now in her late 30's probably won't have the patience for Zelda and would likely find Splatoon's control scheme too complex, but she remembers Super Mario Bros and the incredibly intuitive controls and design method of Mario Maker could very much appeal to her when making/playing levels with her kids, nieces and nephews.

Of course, none of this means much without proper marketing.  Something similar to the first 20 seconds or so of the reveal trailer would be perfect for a commercial:

https://www.youtube.com/watch?v=NLS458ekSEI

But Nintendo should really go a couple of steps further for the holidays and reveal a WiiU with a new sleeker, more aesthetically pleasing Gamepad coupled with a reasonable price drop ($249-$269) that comes bundled with MM (probably pre-installed).  Now add in the variety that Zelda, Starfox, XCX and Splatoon provides and that would give the console the most potential to do much better in every market.

I'd finally buy a Wii U with 3 amibs and a game for $150.

It's too late for anything like that; consumer products that are moving really, really slowly don't suddenly become a lot more popular simply for being cheaper; if there was potential for a 5 million selling year we'd have seen signs of it in the year where Mario Kart and Smash released. It was the same with the Wii's price cut once it had started to slide; it did nothing to put it back on top and the fall continued. The Wii U is quite simply not a popular product and this is due to its design and aim (or lack thereof) and not the price tag. Lowering the price will help any product; it will not produce miracles.

Has everyone forgotten that the cheaper model of the Wii U is/was the one that sold the least by far? It has accounted for a very small portion of total sales and actually sold so few that there are still some in circulation despite no shipments in ages and even being outright discontinued in some regions. Have we also forgotten that the Gamecube was 99$ after only a couple of years on the market?

Price was never the Wii U's main challenge, whoever hasn't realized this by now, simply never will. Besides; the last thing Nintendo needs now is losing more money on the Wii U, they should focus on the 9th gen and squeezing some gains out of the 3DS instead. Their best bet is a comeback in the 9th gen; which might very well be possible, but not if they don't reinvent themselves completely.

MS has way more money to lose and is willing to lose way more money than Nintendo. Nintendo does not mind being a distant 3rd for profits

Nintendo does not need to reinvent "completely" or even slightly. If Wii U had a bit more power to get current multiplatform games it would sell much more.

But even when Nintendo decides not to take a seat in the hardware race next gen the potential next Handheld/console hybrid platform will likely be a success. Nintendo will be able to produce enough games to satisfy all gamers if they can concentrate on one platform and continue with deals like Devil's Third, Bayonetta or FEvs.SMT

This post is so spot on. 

The Wii U at $299.99 is a reasonable price as is (considering it even comes with 2 free games) and is the cheapest of the "new" consoles. If people really wanted one they'd be buying one. But they're not, they're buying the more expensive Playstation 4 or XBox One instead in droves. Mario Kart, Smash Bros., and Mario 3D World have not shifted that dynamic one bit. 

I think it's fair to say the formula of just relying mainly on Nintendo franchises and pushing a family friendly style console just doesn't get you any more than 22 million-ish or so. The GameCube was $99.99 for the entire second half of its lifecycle and it still couldn't crack 25 million. People still overwhelmingly chose the Playstation 2, even kids. 

1. Yes, just a myth. 2. Not true.

It already has the power to get multiplatform games.

Not intending this to sound offensive, but it probably will...

I find that the tendency is for people who want a Wii U but can't afford multiple consoles to be the types that continue to say that it needs a price cut.

If anything, at MAX, I would say a drop to $250 is the sweet spot, putting each system within their respective power tiers (and not necessarily overall value). However, a price drop is not the solution, and never will be despite its inevitable occurrence at some point.

The problem will always be image. The majority of console buyers are not gamers, but what are colloquially termed as "casuals". They tend to go for what they want, not what is necessarily the best purchase. What they want is what they see as cool, and that's where marketing comes into play.

You want Nintendo to sell 5+ mil consoles? Marketing, and proper marketing at that. And fortunately, this year and the next will most likely see the return of titles that can be marketed with relative ease: Starfox, Xenoblade Chronicles X (ex/ to anime fans, Japan), Zelda U, and highly likely the eventual announcement of a Metroid title; all titles that don't exactly exude strictly "family friendly" or "kiddy" themes, especially of marketed adeptly.

but those games arent really casual games. So no matter how well they are marketed they wont push much systems. Most of the people who actually want them have a Wii U already.