The redirect or riposte stunt let you do the trick with only one avoided attack, and it uses your next exchange. The power should be built along those lines.
I actually think that this should just be something you can do...Fate Core has a "Defend with Style" which puts a fragile aspect on an enemy or possibly the scene if you beat their attack by a lot. That lets you do things like deflect an incoming bullet into a spotlight, or have somebody overbalance after missing you, etc. The Dresden books have a number of examples of Harry using his shield spell to deflect attacks in useful ways, and some of his enemies manage the same. We know Harry doesn't have an Riposte type stunt, although I guess with magic you might generate shifts with drawn power to combine a block with a maneuver if the GM is ok with it. (eg, draw 8 shifts for a level 4 block and level 4 maneuver, the maneuver can only be used if someone attacks your block, to simulate Harry angling his shield so a charging enemy goes flying into the air after bouncing off) Might do a "zonewide" block and maneuver to handle multiple attacks until the block is knocked down..12 shifts of power for the same effect)
