What does Nintendo need to do to cure the developer support issue? They need to first recognize it. As someone who has been a fan of Nintendo since the 80's, it pains me to accept that they don't appear to see this as much of an issue. If they did, they would show more interest in matching their competitors. About their competitors, though, I'm not sure they recognize who their competitors actually are. I bet if we asked them, they would name Apple, Google, and perhaps Sony. After all, they show a ton more concern over the mobile market than they do the games one.
I'm slowly losing interest in the NX. Even though all we have are rumors to work off of, the more I hear about it the more I'm convinced they are bound to make the same mistakes as before. Nintendo seems destined to match whatever is currently on the market, go with custom hardware to do it, and have some showcase feature that is the centerpiece to the experience. I love the Wii U, but it is far from a success mostly for the reasons I've listed. Developers may not mind the challenges of working with a unique platform, but businesses hate spending additional resources on a gamble.
I would love for Nintendo to go the extra mile with their home console product. I want to see them embrace some industry standards such as the X86 architecture. Nintendo needs to be a little bold this time like opting to cram some additional hardware power into this box and sell at a small loss. As the consumer, I don't feel good about hearing Nintendo turning a profit from day 1. I need to feel their is a little something special in that box. More to the point, I want to feel that Nintendo has gone the distance in producing a gamer's machine with slick UI, smooth OS, and lots of interesting features.
If Nintendo wants to wow, they can. If they did, I believe they'd go with mainstream hardware and a "modern" online community that demonstrates they understand the competitive gamer's wants and needs. Plus, I'd like to see them do something like strike a deal with Valve and and make the NX into a fully compatible Steambox. If you can't get publishers on board from day 1, then bring them on through someone else's platform from day 1.
But nah, that would require robust hardware and forward thinking that goes beyond your own nose.