Read OP on stock+. It is pretty easy to enable these, search google play for apk.
It regards power modes in build.prop. Wi-fi is not affected. Only rescaning for open wifi when disconected. Once in a minute
Cool, thanks. Confirmed that Stock+ has init.d support
Glad to hear that the powersaving won't prevent WiFi working. I don't really see how that can equal "Phone practically dead when screen is turned off (zero battery loss overnight)" though, as obviously apps (Jitsi, Xabber, etc) have to maintain a connection and send at least keep-alive signals to the server regularly (I don't know what interval they use though) to prevent other users seeing them as disconnected, which must drain the battery somewhat, not to mention if other things happen overnight, like apps autoupdating, etc.
Not that it really matters to me as I have my phone plugged in to charge overnight, so that ensures there's zero battery loss