Well, I would like to see a Take Em All challenge, as long as there are dungeons available for all of the bosses. (Can't remember if Spirit Tracks had that feature or not)
When I defeated the TEA Challenge, I felt... like it was too quick and as if it was just there for show. It was only, like, 10 floors and then a boss, big whoop. There wasn't that much of difficulty of it, and I was really disappointed that it wasn't was challenging, as it should've been. Skyward Sword needs to be more challenging, like, only hard- core Zelda players who always know what's coming next can beat the boss easily, not easy, for the newbies playing. We hard cores need to be challenged and if Skyward Sword doesn't prove to me that it can be difficult and make me smack my TV with the wiimote, (Did that many times with TP, and usually, when I do that, it turns out to the a good game that I love) then I will be a bit disappointed.
As long as it offers TEA challenges to all of the bosses and prove to be a little difficult, I'm happy.