So a couple months ago I saw someone say they were working on power down for iOS 11. They said at the time that their ETA was "1 week later", but since it has been months I decided I'd try and take the project on. I will most likely release in a day or two. It will support any jailbreakable version (so far) above 10.3.
I know CoolStar already released BetterPowerDown, but this one will be free.