The only thing I'll miss are costumes. I still don't get why they removed them :/
Lol what?! You mean no costumes via amiibo for example?
That would be seriously stupid. In MM1 I even made a level around Wii Fit Trainer, called "Stay Fit with Wii Fit Trainer", where you had to jump around as the Trainer in a fast paced level made of treadmills.
Without Wii Fit Trainer that would be half as charming.