Final Smashes

I've tried this before, but it's impossible. You see, what happens is, the amiibo recognizes the Smash Ball as something it needs to get. The same goes for the timer, among other items. But once it gets and activates the item, that's it. It goes back to its normal behavior.

The only way around this is to teach your amiibo to be more aggressive, but there's two problems. First, if your aggressive amiibo goes against a defensive opponent, the aggressive character will be forced to slow down in order to get on the level of the defensive amiibo. Second, your amiibo will likely get mauled in battle due to not being defensive.

Basically, no. Impossible. Keep focusing on defense and perfect shields and that's all you need. The characters with transforming final smashes (Little Mac, Bowser, and Lucario) are all really good already.