So let me just ask you and EO: What do YOU think they would have to do to get third parties back on board/
If I knew that I would be CEO of Nintendo, now wouldn't I? I'm not saying this idea will fail, don't get me wrong, but personally I don't think many hardcore gamers will just move to a Nintendo console just because they created this controller, at least those who already have a 360 and/or PS3.
The first thing I would definitely do is change the name of the console and stop trying to ride the Wii's success. You want to start fresh and attract third party devs and hardcore gamers? give it a new name (like they've done before).
The second thing I would do is not make a console that is handicapped in one area like past nintendo consoles have. The N64 was using cartridges when everyone else was still with CDs. The Gamecube was using discs that could hold how much? 2gb? didn't the competition have DVDs that could hold almost 5gb of data? The wii had its focus on waggle and had pretty bad online when compared to others. It also tried to capture casual gamers (and succeeded) which made hardcore gamers run away from it.
Basically make a console that has a great online, good storage, great media, same graphics as competitors AND add that special thing (which in this case is the touchscreen in the controller). Also don't market it as a casual system. Nintendo needs to hope that Sony nor Microsoft will make a really powerful console.
Edit: This, definitely this:
I'm sure most Nintendo games will opt to use the WiiPad, but I'm sure many third-party multiplatform games will let you use Pro Pad or the WiiPad. Even if they do choose to add some touch screen features, I wouldn't be surprised if they let you play the game in non-touchscreen mode, as if you were playing on the PS3 or 360.
Force third party devs to at least put some use on the touchscreen but still allow us to play games without it.