I've said it before but...

A diablo-esque game where you use amiibo data from other games to decide build a character. Once your character's stats and appearance is set by a combinations of amiibo, scanned data, and class choice, you can use it to battle hordes of enemies through famous enemy strongholds from Nintendo's history. You and up to three friends can team up to raid Bowser's castle and fight through hordes of koopas, hammer bros., chargin chucks, dry bones, and magikoopas. Make a giant Blargg a sub boss, and fight a giant Bowser as the raid's final boss.

There are others that work too. Ganon's Tower, a Space Pirate ship, Andross's stronghold on Venom. The benefits to a game like this is insane. It can keep growing, can promote upcoming stuff, and encourages players to buy multiple nintendo games. It's almost a crime that they haven't had this in mind from the start.