IMO ios4 remains the most exciting OS update to date. It was the OS which introduced folders for apps, amongst other things. For the first time we could group apps with similar like features together. Extremely useful and not gimmicky at all. And it's something we all take for granted today.
That's what I'm hoping for in ios12. Something new and significant, which will add to the experience but not be gimmicky and/or of little use. Yes I want stability and a buttery smooth UI, but I think the OS is due for it's next ios4-like update.
With regards to the little things, what I would like to see are:
Dark mode. Waiting for the day a class action against Apple is filed for eyestrain, blindness or partial loss of vision.
Get rid of the 10% and 20% battery warning indicators after you have plugged your charger into your phone. I can understand the need for them when the battery is draining, but why have them pop up after I have plugged in the charger and its counted up to 10%? Extremely annoying especially when I'm watching a stream and the stream stops because my phone is warning me that my battery is back up to 10% again. Seriously.
Get rid of the volume bar which is smack bang in the middle of the screen when you toggle the volume. As many others have suggested, put it at the top.
I would like to see some customisation. People talk about not being fussed looking at the same thing all the time, but I bet they wear different clothing most days and change their hairstyle from time to time. A change is as good as a holiday. Does not have to be over the top but grid layout and some other things would be nice. Our iphone is probably the thing we use the most in our life so why can't we customise it to suit ourselves?
Merge the reminders app with the calendar app. One relies on the other so I don't see the need for a seperate app.
Have all the settings for the camera within the camera app.
Ability to lock the screen in landscape mode.
Would like an app where you can message Apple directly for any troubleshooting issues. Maybe implement that into the tips app. The app could allow for media to be sent through so you could send a screen shot or recording of your problem and they could message you back with a solution. And if a genius bar appointmwnt is required, you could book it directly through the app.
Would like a dedicated one stop shop multimedia editing app. The ability to do anything you want to a picture or video, for example, rotate a video because it was flipped when you recorded it, speed it up or down, add stickers to videos, etc, add filters, etc. All in the one native app.
Would also like the ability to rearrange media in the gallery. The abiluty to loop a video would also be good. I do have a loop app.