Wasn´t a rumour lately that they were already working on a title like that? I can´t remember where I saw it.
It makes a lot of sense and it would be a shame if they don´t do it.
What I´d love to see is a full game (not mini games please) and the option to play as any of the amiibo you want. I know it would be very difficult, and maybe they could start with only a few of them, but I would love to play as King Dedede, Wario, Charizard, Chibi Robo, Green Squid, Pink Yoshi, Megaman... They would sell millions of that games, and if not, at least they would sell millions of amiibo, as that would be the thing that would made me buy dozens of amiibo and I´m sure people would jump as well.
Right now, amiibo are only for decoration for me, so that would be great.