[Xperia Z3 Compact General] Nazo:
Another missing option: any control whatsoever of emergency alerts. I was just disturbed earlier by receiving an emergency alert and it turned out to be the standard test broadcast and not even so much as an amber alert. I need to receive only the most extreme alerts only so I find this to be very very unpleasant. It looks like SONY has opted to remove the built in controls in the system settings or stock messaging app in favor of a separate emergency app. Previously apparently they did let you change the settings in their Lollipop ROM (I was using CyanogenMod up until this 6.0.1 release, so can't really attest to that) but I go to the emergency app in this and it has absolutely no settings or controls, just a list of the previously received alerts (so far just that test alert for me.) Normally test alerts shouldn't even be on by default, so someone dropped the ball here I guess.

EDIT: Apparently Google's own Messenger app can be separately downloaded: https://play.google.com/store/apps/details?id=com.google.android.apps.messaging&hl=en It has a setting for this. I'm not sure if this is system-wide, but I'll just switch to their app because there's not really any reason not to I guess.

EDIT2: I had manually loaded CellBroadcastReceiver.apk from CyanogenMod's packages (probably more or less AOSP standard, but I had CyanogenMod handy.) Apparently this was the reason I had that option. I removed it and the option was gone. Put it back on and the option has returned. It looks like it has to be loaded as a system app. I froze SONY's Emergency Alerts app. So far so good. I'll have to wait until the next real emergency alert to really know for sure. I can't tell if this specifically requires their Messenger app or not (I think maybe since I still have nothing at all in the SONY app for this.)

EDIT2: BTW, on the battery saving stuff, turning off WiFi -- as already discussed -- won't help much at all. In fact, it's mostly useless. In fact, if you leave data on and things start using it, that will hurt more. As far as 3g versus 4g goes, it takes significantly longer on 3g for even a small amount of data so while it uses less power, it uses it for longer and the net result is very little savings there too. To my mind at least, it's a much better solution to use Greenify to keep the apps I don't actually need running in the background all the time -- particularly those that like to phone home, but have no actual need to do so -- from actually running. (It doesn't work like a task killer killing tasks on a timer where they just restart a little bit later using more resources in the process of doing so but actually closes them down and blocks them from autostarting all the time, though I think maybe it allows them to wake up for just a bit from time to time.) This also can help keep things running a bit better even when not on battery by clearing up some resources since you don't have practically everything basically running 24/7.

On SD card access, I don't think Google plans to change anything for the better there. They've basically decided that it's "necessary" for security to do things this way. I guess mostly because it requires the user to explicitly grant access. But also, Google has been wanting to eliminate SD card support for ages (I guess OEMs pressuring them to let them do the Apple thing? Or maybe they just want to be lazy and not have to bother doing the work to support them. I don't know. But as it's Linux based I don't buy excuses that it's supposed to be really hard or whatever.)