Wouldn't it be simpler to just redirect it?

It would, but this does allow for interactions with cards like Guile that care when spells are countered.

So what happens when you target a Serra Angel with this?

Fun times?

At the moment, the game falls over and dies. They still haven't added the utterly obvious rule that a copy of a permanent spell enters the battlefield as a permanent token.

I tweeted Mark Tabak about that once, and he never replied. It would make perfect sense, of course, but since there are no cards that do it there's no need for a rule.

Also, redirecting doesn't quite convey the same thing, in that you're the controller of the new copy. That means this is essentially Commandeer with no pitchout option, or to be closer to the mana cost, Swerve + Swipe (assuming the latter is ever printable as is).