I don't understand why he feels the need to recount Nintendo's history in an open letter to Nintendo - does he really think they don't know their own story? This video doesn't seem like a letter to Nintendo at all, except for the last minute.
In terms of his actual message to Nintendo, it basically boils down to - make good games, make good niche games, and help third parties - nothing particularly novel there.
If I were going to give a message to Nintendo, right now it would be something along the lines of "WHAT THE HELL ARE YOU DOING?"
They launch a mobile Fire Emblem game with the purported purpose of enticing mobile games to purchase Nintendo hardware after getting hooked on their exclusive franchises, while at the same time having practically ZERO 3DS consoles available in the US for sale? They can't manage to stock shelves with a console that is 6 years old?? Not to mention the NES Classic, which should be making the company boatloads of cash but is instead still impossible to find 2 months after Christmas?? With Switch, they start preorders seemingly out of nowhere which sell out immediately, leading many (myself included) to conclude that the impending launch will be just as short stocked and mismanaged as the recent Classic debacle. Have we seen any accountability from them for any of these failures? Or for the Wii U failure? I don't recall seeing any public firings or mea culpas after having burned their fans over and over again recently, and it's making me angry.
Here's my advice for Nintendo:
1) Fire someone high up responsible for this supply travesty and issue a public apology to all of the fans who have been clamoring trying to buy a 3DS or NES Classic for the past 4 months, promise to fix your supply chain issues, and spend some money to FIX IT.
2) If you're going to start preorders for your new thing that people might want, announce the start time and where to preorder days in advance so people can plan in advance.
3) Start developing (or if you are already developing, announce) several titles that would previously have been 3DS titles but are coming to the Switch. I'm talking about $40 titles like Fire Emblem, Mario & Luigi, Advance Wars, whatever - games that are traditionally for handheld consoles at handheld prices. This will show developers that you are serious about the mobile aspect of Switch and hopefully bring the 3DS faithful into the fold. If you lead the way showing there are 2 viable price points for Switch software, 3rd parties will follow.