iO7 Live BLUR without duplicating

If you're not going to duplicate the data that needs to be blurred, then you'd need to blur the actual source in the exact spot you need the effect. There's no other way to do it, so I wouldn't get too bogged down trying not to duplicate.

Is your target a device app? The quality of the blur and speed it appears is so fast it'd probably only be possible in Stage3D, WITH cache (GPU uploading is expensive, let alone processing time).

Have you attempted to measure the speed of duplicating a clip and either adding a blur filter or running the calcs in BitmapData to see what performance you get?