Go third party. The hardware is unnecessary.

I would push back the NX a few years. I would focus on 4K graphics, and having a system players want to buy. Drop the Wii U's price to $199.99. Create a new line of Amiibo games, like a RPG and racing game. I would look into purchasing franchises that we should own, like Mega man, Monster Hunter, ect.

Focus on better hardware, and work on creating more diverse IPs.

Oh, and focus more on amiibo, cause at least it's keep Nintendo afloat.

PS3 could come back because there was nothing fundamentally wrong with its design. It was simply a little too expensive at first but once the price came down it had up to date technology and good third party support.

Wii U is massively outdated hardware (tablets and phones will soon overtake its horsepower, and its waaaay behind the PS4/XB1) with almost zero third party support.

You have a point. NoA, in general, has not been as great as it used to be. Marketing towards everyone besides children would be better. NoA needs to find a way to reach out to broader audiences while maintaining their fun and family-friendly appeal. Maybe spend a little more income on things besides advertising specific games like Splatoon or Mario Kart. Even use their ownership of the Seattle Mariners to their advantage (even though the team is not that good right now to really warrant making them must watch TV beyond the typical fanbase).

As for what I would do:

-I would try to ask all of the development teams to create new ideas for old and new IPs. Also, continue doing collaborations with third parties.

-I would also be a little less firm on my control of the IPs, though strong enough to ensure that whatever is being done will maintain the integrity of the IPs that are being represented. We all know Nintendo has done certain things because they want to ensure control of their IPs. I don't blame them because their IPs are some of the most well-known IPs in existence. Mario and Pikachu are as well-known as Mickey Mouse at this point. Nintendo wouldn't be where they are right now if it weren't for their IPs. However, being a little less firm would at least decrease the tension between those who are little frustrated with Nintendo's control of their IPs.

-Build relationships with not only third-parties and indies, but also content creators. They've already started with YouTube content creators such as Jwittz, The Completionist, iJustine, Andre the Black Nerd, Game Theorists, etc. They even made certain content creators Nintendo ambassadors (I know that because I've been following a few YouTube content creators who can request review copies of games they're interested in).

-Do more live events outside of E3 Digital Events and Nintendo Directs. This year, there was the Nintendo World Championships, a live demonstration of Xenoblade Chronicles X, and a Splatournament along with Treehouse Live at E3. Heck, there was even an event that invited a variety of personalities in promotion of Splatoon's upcoming release. In a way, this does involve my previous point of content creator relationships. 

-Take a little more risk in terms of hardware. Not just in innovation (like the Wii, DS, 3Ds, or Wii U), but also in other areas. Find a way to create hardware that shows innovation and modernization. Hopefully, NX will be able to do something like that.

Relax the stance on video game content such as sex and drugs, I would also create hardware that is either as or more powerful than the competition and get 3rd parties on board. This has been one thing that really annoys me about Nintendo, nothing against their games but I can't justify spending £250 on a wiiU just to play Mario maker, splatoon and zelda on......

First and only thing i'd do is buy capcom then get a successor.

Sell the company to Sony and retire on 10's of billions of monies.

First thing I'd do is hold a board meeting with all the Japanese men. I'd gather them around the table and I'd basically say the following.

"Gentlemen, I know that this company has be run in a different manner since Yamauchi passed away many years ago, but from now on, we are going to fight. Our company will no longer stand by and be marginalized and molded by our competitors. We are going to run very detailed market research going forward and we're going to analyze what the current industry's consumers want and then, we are going to attack on all fronts and meet our competitors head on. The blue waters of the past are gone. From now on, we are going to swim the waters of our competitors and win at any means necessary."