There was a noticable performance hit, but my phone is 3+ years old. It likely would not be as much on a newer phone.
http://forum.xda-developers.com/xposed/modules/xposed-appops...
Hmm? I can do exactly this in the Privacy Guard settings.
You can choose which permissions you want an app to have and which you don't. You can also set to Ask every time as well as just blanket blocking/.allowing permanently.
As far as I'm aware you just long-press the app name in order to get to the more granular permissions controls.
There's nothing else I'm aware of that needs these long presses to get more options, save the stuff that Android has anyway.
HN rate limits replies when comments are nested. You either wait for the reply link to show up, or you clicky the time stamp.