Like the example described, what I want the power to be able to do is create the sound and look of something that just isn't there. Such as copying oneself 3 or 4 times, to make it difficult to hit the right one, or creating the image of a menacing thug for backup, or making it look like there's a fence blocking the alleyway. All of these cases, what is perceived simply isn't there, it's just illusion.
Copying yourself to be harder to hit is definitely a block, that's quite simple.
The thug could be a maneuver to tag on an intimidation attack. Or an intimidation attack itself, using the power.
The fence could be many things, too. Easiest, it is a block. Just because it isn't real doesn't mean someone would not be stopped by it, or redirect his course, because he just doesn't have time to test it out while fleeing. Insubstantial or not, the fence blocks his escape. Or it can be done as a maneuver and help you on the pursuit.
It helps if you think about the things you want to do in terms of their impact on the story, not in terms of what a character would be physically doing. I could put up a block using intimidate, and all I am doing is sitting at my desk, raising an eyebrow. But I am attempting to intimidate my opponent so he can't do anything. Keeping someone from doing something in mechanical terms is a block, so that's what I'm doing. Of course, the same gesture can be an attack to make my opponent afraid of me in a social conflict.
The power could merely be a way o substitute deceit for a variety of skills in a variety of situations. Then again, that's what Glamours does as well. A bit less so, maybe, but since you are taking out veils, that should equal things out well and good.